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A Manual Of Physiology | by Gerald F. Yeo



The present volume has been written at the desire on the part of the Publishers that a new elementary treatise on Physiology should be added to the series of admirable students' manuals which they had previously issued. In carrying this desire into execution, I have endeavored to avoid theories which have not borne the test of time, and such details of methods as are unnecessary for junior students. I do not give any history of how our knowledge has grown to its present standpoint; nor do I mention the names of the authorities upon whose writings my statements depend. I have also omitted the mention of exceptional points, because I find that exceptions are more easily remembered than the main facts from which they differ; and, since we must often be content with the retention of the one or the other, I have tried to insure that it shall be the more important.

TitleA Manual Of Physiology
AuthorGerald F. Yeo
PublisherP. Blakiston, Son & Co.
Year1889
Copyright1889, P. Blakiston, Son & Co.
AmazonManual Of Physiology

By Gerald F. Yeo, M.D.Dubl., F.R.C.S, Professor Of Physiology In King's College, London, Etc.

Fourth American

From The Second English Edition.

With Three Hundred And Twenty-One Illustrations And A Glossary.

A Manual Of Physiology 1
-Preface To The Second Edition
In preparing this edition, I have done my utmost to correct inaccuracies and remove obscurities. The changes rendered necessary by recent research have also been made. Some parts have been rewritte...
-Comparison Of The Metrical With The Common Measures
Measures Of Length In English Inches. In English Feet = 12 Inches. In English Yards = 3 Feet. In English Fathoms = 6 Feet. In English...
-Chapter I. The Objects Of Physiology
Biology, the science which deals with living beings, may be divided into two branches, viz.: i. Morphology, which treats of the form and structure of living creatures; and, 2. Physiology, which attemp...
-General Characters Of Organisms
The term organism, which is commonly used as having the same meaning as living being, owes its derivation to the complexity of structure common among the higher forms of life, which are made up of sev...
-2. Chemical Composition
There are no characters in the chemical composition of the textures of organic beings which can be said to be absolutely distinctive or to separate them from inorganic matter. No doubt their chemical ...
-3. Vital Phenomena
The so-called vital phenomena which take place in the textures of organisms are, for the most part, performed by the agency of the living cell elements, in which we can recognize independent manifesta...
-Chapter II. General View Of The Structural Characters Of Animal Organisms
The parts played by Cells in the functions of living beings are so many and so important that it is necessary at the very outset to consider the properties of the Fig. i. individual elements somewhat ...
-I. Protoplasm
Protoplasm is commonly seen to be a colorless, pale, milky, semi-translucent substance, more or less altered in appearance by various foreign matters lying in it. These latter also give it a granular ...
-2. The Nucleus
The majority of independent masses of protoplasm, and all highly organized cells, contain one or more nuclei in their substance. The nucleus is sharply marked off from the protoplasm, and is supposed ...
-3. The Cell Wall
It has already been stated that the most active cells, such as are found in the earliest stages in the life of an organism (embryonic cells), have no inclosing membrane or cell wall. But in the more a...
-4. Cell Contents
Regarding protoplasm as the essential living part of the cell, under this heading will come only those extraneous matters which are the outcome of protoplasmic activity. The cell contents which are...
-Varieties Of Cells
Great varieties of cells are found in the various mature tissues of the higher animals, all of which have passed through the stage of being a simple nucleated mass of protoplasm in the earlier periods...
-Tissue Differentiation
The first stage in the existence of any organism, from the simplest form of plant to man, consists of a single cell (in animals called the ovum or egg), which differs in no essential points of structu...
-Tissue Differentiation. Continued
The middle germ layer (mesoblast) is derived from the upper (epiblast) and lower (hypoblast), the relative amount contributed by each being doubtful. From the earliest period the middle layer has dist...
-Nerve Tissue
The great nervous centres are formed from the cells of the epiblast, which, in the earliest days of the embryo, form a longitudinal furrow, which sinks into the cells of the mesoblast. By the rapid gr...
-Muscles Or Contractile Tissues
When changes take place in protoplasm adapting it specially for contraction, it is termed muscle tissue. The large masses of this tissue attached to the skeleton so as to move its various parts, form ...
-Mucous Tissue
In certain parts of the embryo and in some of the lower animals a kind of connective tissue is found in which there is but little intercellular substance, the mass of the tissue being thus made up of ...
-White Fibrous Tissue
The cells of the last described variety may become differentiated by a process of fibrillation. The growth of the cells leads to the formation of a fibrillated substance which ultimately forms the gre...
-Yellow Elastic Tissue
In some parts of the body a kind of intercellular substance is formed, which differs in many respects from the foregoing. It is highly elastic, does not give gelatine on boiling, and is not affected b...
-Cartilage
In this tissue the intercellular substance secreted by the cells is hard, and forms in the earlier stages of its development cases or cell walls for the cells. These cases subsequently increase in thi...
-Bone
This is the most marked differentiation of the connective tissue group. The intercellular substance is characterized by containing a great quantity of earthy or inorganic matter (65 %), which gives th...
-Endothelium
Wherever a surface occurs in the connective tissues it is generally covered by a single layer of thin cells with a characteristic outline, which can only be made visible by staining the intervening ce...
-Chapter III. Chemical Basis Of The Body
It seems natural to commence the description of the molecular changes that take place in the various tissues and organs of the body with a brief account of the chemical composition of the most charact...
-Class A. - Nitrogenous. Group I. - Plasmata
Under this group may be placed a variety of substances which must be acknowledged to exist in the living tissues as complex chemical compounds, of whose constitution we are ignorant, since it is alter...
-Group II. - Albuminous Bodies
It is difficult to say how far these bodies exist as such in the living organism, but they can be obtained from nearly all parts, particularly those which contain active protoplasm, and after its deat...
-Classification Of Albumins
Under the head of the albuminous bodies we find several classes which differ from each other in slight but very important points. The first class may be called - (A) Albumins Proper, Or Native Albu...
-Group III. - Albuminoids
These are the outcome of nutritive modification of protoplasm, and may be said to be directly manufactured by that substance, and to be specially adapted to meet the requirements of certain textures d...
-Group IV. - Products Of Tissue Change. Intermediate Or By-Products
These are protoplasmic manufactures destined for some useful purpose, but they do not long exist in their original form; being often broken up into other compounds, they are reabsorbed, or pass away w...
-Bile Salts
Two acids exist in the bile united with soda to form soluble soap-like salts. They may be recognized by the purple-violet color produced by cane sugar and sulphuric acid at a temperature of about 700 ...
-Effete Products
These, as has been stated before, are generally the outcome of the active chemical changes necessary for the growth and vitality of the living protoplasm, and are for the most part soon eliminated by ...
-Class B. - Non-Nitrogenous. Group V. - Carbohydrates
Carbohydrates (general formula, CmH2nOn) are bodies in which the hydrogen and oxygen exist in the same proportion as in water, the carbon being variable. The following examples of this group are met w...
-Group VI. - Fats
These bodies have the same elements in their composition, but the hydrogen and oxygen have variable proportions - not that of water. Fats are found in large masses in some tissues, and also as fine pa...
-Inorganic Bodies
Water (H20) is present in nearly all tissues in larger proportion than any other compound, making up about 70 per cent, of the entire body weight. The amount in each texture varies, the different tiss...
-Salts
A large number of salts occur in the tissues, generally in small quantity, in solution. In the teeth and in bone tissue salts exist in the solid form, and in much greater proportion than in any of the...
-Chapter IV. The Vital Characters Of Organisms
The manifestation of so-called vital phenomena in man forms the subject-matter of the following chapters, and some explanatory definition of the vital characters of the simpler organisms will be usefu...
-The Vital Characters Of Organisms. Part 2
From the foregoing description of the manner in which protoplasm responds to external stimuli, it may be gathered that it is capable of appreciating impressions from without; indeed, it can be said to...
-The Vital Characters Of Organisms. Part 3
It has already been stated that the material protoplasm, which forms all active cells, is capable of carrying on the many functions required for the independent existence of simple creatures. It will ...
-The Vital Characters Of Organisms. Part 4
We next come to forms of fungus, which set up a process very like putrefaction, such as the yeast plant, Torula cerevisia, which causes alcoholic fermentation in sugar solutions. In the torula an exte...
-Chapter V. Food
The continuation of life depends on certain chemical changes which are accompanied by a loss of substance on the part of the active tissues. This loss must be made good by the assimilation of material...
-Classification Of Food Stuffs
There are two portals, namely, the lungs and the alimentary canal, by which new materials normally enter the animal body. Within the lungs the blood comes into close relation with the air, and take...
-Food Requirements
Chemically, foods are composed of a limited number of elements similar to those found in the animal tissues, viz., carbon, oxygen, nitrogen and hydrogen, together with some salts. If nothing more were...
-Milk
For a certain period of their lifetime the secretion of the mammary gland forms the only food of all mammals, and it is the one natural product which when taken alone affords adequate nutriment. It...
-Milk Tests
The specific gravity of milk gives an easy measure of the solids in solution, but unfortunately it gives no accurate estimate of the amount of fat suspended in the emulsion. Therefore, to test milk ad...
-Meat
We use the flesh of the vegetable-feeding mammals and birds that are most easily obtainable, and many kinds of fish. The invertebrate animals, mostly shellfish, needly hardly be mentioned in a physiol...
-Eggs
Eggs consist of two edible parts; one, the white, composed of albumin, and the other, the yelk, chiefly made up of fat. The white is a concentrated, watery solution of albumin, held together by del...
-Vegetable Food
Vegetables differ from animal food - (1) In containing a much greater proportion of material which for man is indigestible (cellulose), and a less proportion of nutritive material. (2) The perce...
-Cereals
The most valuable forms of vegetable foods are those obtained from the seeds of certain kindred plants {Graminacece) - wheat, rye, maize, oats, rice, etc.; which when ground are used either as whole ...
-Green Vegetables
These contain some starch, sugar, dextrin, salts, and minute quantities of proteid, and are of small nutritive value. Potatoes contain very little proteid, but a considerable quantity of starch, up...
-Salt
Great varieties of salts are taken into the system, of which chloride of sodium forms the largest proportion. These have, no doubt, very important functions to perform, in entering into combination wi...
-Chapter VI. The Mechanism Of Digestion
The acts of digestion may be divided into mechanical and chemical processes. Under the mechanical processes come the arrangements for the subdivision, onward movement and general mixture of the food. ...
-Mastication
In man, the introduction of food into the mouth is generally accomplished by artificial means, so that the biting teeth (incisors) and the tearing teeth (canines) (Fig. 46) are comparatively little us...
-Structure Of The Teeth
The exposed part of the teeth is covered by a dense substance of flinty hardness called enamel, which is developed from the epithelium, and consists of hexagonal prisms set on end, which are really mo...
-Deglutition
The next step is swallowing. When the food is sufficiently triturated and moistened, it is collected together by means of the tongue and placed upon the upper surface of that organ, which becomes conc...
-Nervous Mechanism Of Mastication And Deglutition
- The voluntary influences which regulate the motions of the muscles of mastication pass along the efferent branches of the fifth nerves (trigemini) which accompany its inferior division. The muscles ...
-Motion Of The Stomach
The stomach and greater part of the intestinal tract move freely within the abdomen, being covered by the smooth serous lining of that cavity, which also keeps in position, so as to restrict their mov...
-Nerve Influence On Stomach Motions
The stomach has nerve connections with the cerebro-spinal axis through the vagi, and the splanchnic branches of the sympathetic, and in the walls of the organ itself are numerous ganglion cells. The s...
-Movements Of The Intestines
The muscular coats are somewhat differently arranged in the small and the large intestines, but have the same general relation to each other, viz., a thin longitudinal layer lying externally, next the...
-Mechanism Of Defecation
This is a point of much importance, for the evacuation of the lower bowel is intimately connected with feelings of comfort and health, and in illness the insuring of its accomplishment forms an essent...
-Nervous Mechanism Of The Intestinal Motion
Many points in the nervous control exerted over the intestinal muscles are obscure. We know that intestinal movements which are peristaltic in their nature occur in a portion of intestine removed from...
-Chapter VII. Mouth Digestion
The cavity of the mouth is lined by a bright red mucous membrane, which is continuous with the skin at the lips. It varies in structure in different parts of the buccal cavity, and in its general cons...
-The Characters Of Mixed Saliva
The liquid in the mouth is a mixture of the secretion of the salivary glands with that of the small, purely mucous glands. It is a slightly turbid, tasteless fluid, of a distinctly alkaline reactio...
-Collection Of The Secretion
Ordinary mixed saliva may be easily collected by chewing some insoluble material, such as a bit of rubber tubing, and collecting the fluid which the motion causes to be poured into the mouth. The c...
-The Method Of Secretion Of Saliva
Under ordinary circumstances very little saliva is secreted, only sufficient being poured into the mouth to keep the surface moist. When, however, food is introduced into the mouth, and the process of...
-The Method Of Secretion Of Saliva. Continued
The reflex stimuli which were supposed to be elicited through the medium of the submaxillary ganglion, probably depended on the escape of the stimulating electric current used, and the reflexion from ...
-Changes Undergone By Food In The Mouth
Food when taken into the mouth undergoes two processes, which are inseparable and simultaneous in action; viz., mastication and insalivation. The mechanism of mastication has already been discussed...
-Chapter VIII. Stomach Digestion
The surface of the stomach is covered by a single layer of cylindrical epithelial cells which also line the orifices of the numerous glands with which the mucous membrane is thickly studded. This sing...
-Characters Of Gastric Juice
The gastric juice is a clear, colorless fluid with strongly acid reaction. It contains.5 per cent, of solids, its specific gravity being 1002. The amount secreted in the day is extremely variable, and...
-Method Of Obtaining Gastric Secretion
Formerly, attempts were made to obtain gastric juice by inducing a dog, while fasting, to swallow a sponge, and withdrawing it when saturated with the gastric secretion; or a fasting dog, allowed to s...
-Action Of The Gastric Juice
The gastric juice has in the absence of mucus no effect on the carbohydrates, and probably the amylolytic fermentation set up by the saliva is impeded, if not completely checked, by the free acid in t...
-Action Of The Gastric Juice. Continued
There can be little doubt that the conversion of proteid into peptone is normally brought about by the pepsin, which acts as a ferment, in some way or other facilitating a process which without it is ...
-Chapter IX. Pancreatic Juice
The copious secretions of two of the largest glands of the body - the pancreas and the liver - are poured into the duodenum. This is the widest part of the small intestine, and the extent of the surfa...
-Structural Changes In The Cells During Secretion
During the period of rest, i. e., no secretion flowing from the duct, and the gland being pale, the gland cells in the acini undergo a change which may be compared with that observed in the cells of t...
-Pancreatic Digestion
The pancreatic juice is, of all digestive fluids, the most general solvent. It acts upon the three great classes of food stuffs which require modification to enable them to pass through the barrier th...
-Chapter X. Bile
The liver has two chief functions,* which are so distinct in their ultimate object that they may be conveniently described separately. One of these, namely, the secretion of bile, is mainly excrementi...
-Structure Of The Liver
On the surface of the liver are seen with the naked eye small rounded markings about the size of a pin's head, which give the organ a mottled appearance. This is much more striking in some animals (gi...
-Method Of Obtaining Bile
For most practical purposes the bile from the gall bladder of recently killed animals is sufficient. The bile pigments and cholesterin may be conveniently obtained from the gall stones so often found ...
-Composition Of Bile
The bile of man and carnivorous animals is of a deep orange-red color, turning to greenish-brown by decomposition of its coloring matter. In herbivorous animals it has some shade of green when quite f...
-Tests For Bile
The most important constituents of the bile, viz., the bile acids and pigment, may be detected by appropriate tests, which are in common practical use: - 1. Pettenkofer's Test For The Bile Acids ...
-Method Of Secretion Of Bile
The secretion of the liver varies less in the amount formed at different times than that of other digestive glands. Although the changes in the rate of its secretion are not so marked, they follow the...
-Functions Of The Bile
1. Neutralizing And Precipitating Acid Peptones When the acid contents of the stomach are poured into the duodenum and meet with a gush of alkaline bile, a copious cheesy precipitate is formed whic...
-Chapter XI. Functions Of The Intestinal Mucous Membrane
Two distinct varieties of gland are found in the small intestine. Those known as Brunner's glands are localized to the submucosa of the duodenum; they are insignificant in number when compared with th...
-Functions Of The Intestinal Juice
All the properties of the secretion of the pancreas have been accorded to the intestinal juice. It is said to have a ferment, capable of being extracted with glycerine, which can convert cane sugar an...
-Putrefactive Fermentations In The Intestine
With the air and saliva which are swallowed mixed with the food, large numbers of the lower organisms existing in them are introduced into the alimentary canal. The effect of these organisms is to ...
-Chapter XII. Absorption
The nutritive materials must be distributed to the textures and organs in order that the food stuffs, when altered by. the various processes described under digestion, may be of any use to the economy...
-I. Interstitial Absorption
The blood flowing through the body in the delicate capillary vessels yields to the various tissues a kind of irrigation stream of plasma, which leaving the capillaries permeates every tissue and satur...
-Lymphatic Glands, Etc
Along the course of the lymphatic vessels numerous small bodies called lymphatic glands or follicles are found, which are composed of a delicate trelliswork of adenoid tissue, packed with nucleated pr...
-Lymphatic Vessels
There are various modes of origin of the lymphatic vessels which are more or less characteristic of the different parts in which they occur. Fig. 87. Endothelium from serous surface without sto...
-II. Intestinal Absorption
The intestinal absorbents form a special department of the lymphatic system aiding nutrition. On account of the white chyle seen as a milky fluid through their transparent walls, they have been called...
-Mechanism Of Absorption
Formerly absorption was supposed to take place by means of the blood vessels alone. After the discovery of lymph and chyle vessels by Caspar Aselli the belief in the direct absorption by the blood ves...
-Lymph And Chyle
As these two fluids are generally mixed in the thoracic duct, whence the lymph is commonly obtained for examination, we may discuss them together, though the lymph might more properly be considered wi...
-Movement Of The Lymph
In some of the lower animals small muscular sacs occur in the course of the main lymph channels, which pump the lymph into the great veins by contracting rhythmically, much in the same way as the hear...
-Chapter XIII. The Constitution Of The Blood
In all animals, except those which form the lowest class (Protozoa), the distribution of the nutritious materials to the various parts of the body, as well as the collection of the effete matters prio...
-Amount Of Blood In The Body
The total amount of blood has been estimated to be from 1/13 to 1/14 of the body weight for an adult man, and somewhat less for a newborn child. Much difficulty has been found in arriving at an acc...
-Physical Construction Of The Blood
As already stated, the blood is not really a red fluid. It is seen with the microscope to be made up of a clear fluid called plasma or liquor sanguinis, which contains an immense number of little disc...
-Plasma
The fluid part of the blood, plasma or liquor sanguinis, is of a pale straw color, when pure and free from the coloring matter of the corpuscles, and of slightly less density (p. 215). Unless speci...
-Chemical Composition Of Plasma
On account of the rapid spontaneous formation of fibrin and serum when the plasma is removed from the body and allowed to die, the exact chemical condition of the liquor sanguinis during life cannot b...
-Fibrin
Fibrin may be procured either from plasma or blood by whipping, and then washing the insoluble product with water. When fresh it has a pale yellow or whitish color, a filamentous structure, and is sin...
-Serum
This name is given to the clear fluid which oozes out of the clot of plasma. It only differs from the latter in its chemical composition in so far that fibrin is separated from it. Though chemically t...
-Chapter XIV. Blood Corpuscles
The relative number of red discs to the colorless cells is said to be, on the average, 350 to 1. This is true of the blood drawn from the fine vessels by puncture. While in the vessels the blood must ...
-The Colorless Corpuscles
The colorless cells of the blood, commonly called the white corpuscles, differ in no essential respect from the pale round cells which are found in most of the tissues of the body. They exist in large...
-Origin Of The Colorless Blood Cells
Since such an ordinary circumstance as a hearty meal can materially influence the numbers of the white corpuscles, it would appear that they must be usually undergoing rapid variations in their number...
-The Colored Corpuscles
The red discs were discovered in the human blood by Leuwen-hoek, about 1673. They give the red color which characterizes the blood of all vertebrated animals (except the amphioxus), but are not found ...
-Chemistry Of The Coloring Matter Of The Blood. Oxyhemoglobin
Of the chemical constituents found in the blood corpuscles, the coloring matter is by far the most important. To it alone the blood owes one of its most important functions - the respiratory. Oxyhe...
-Methamoglobin
When a solution of oxyhaemoglobin is exposed to the atmosphere for a few days its color changes to a dingy brown, and it takes up more oxygen than it previously contained. The new product is called me...
-Decomposition Of Hemoglobin
Haemoglobin may easily be broken up into two constituents - namely, (a) a colorless substance which is nearly related to the class of proteids called globulin, and (b) a blackish-red amorphous materia...
-Haematin, Etc
Haematin is a secondary product, being the result of oxidation of a substance called hcemochromogen, which is the first outcome of the decomposition of the haemoglobin by acids or strong alkalies. Hae...
-Haemin
Haematin unites with hydrochloric acid to form a crystallizable body called haemin or hydrochlorate of haematin (Teichmann's crystals). If blood or dry haematin be mixed with a small quantity of co...
-Globin
This name has been given by Preyer to the proteid part of the haemoglobin, on account of its slightly differing from globulin, though it resembles it in being precipitated by the weakest acids, even c...
-Chemistry Of The Stroma
The stroma forms only about 10 per cent, of the solid parts of the corpuscles, the rest being haemoglobin. The proteid basis of the stroma is probably made up of a globulin, also containing lecithin, ...
-Development Of The Red Discs
In the early days of the embryo the blood vessels and corpuscles appear to be formed at the same time from the middle layer of the blastoderm (mesoblast). They first consist of round, nucleated, color...
-The Gases Of The Blood
These are present in two conditions: (i) dissolved in accordance with well-established physical laws,* and (2) chemically combined. But since those present in the latter state are but loosely combined...
-Chapter XV. Coagulation Of The Blood
In speaking of the chemical relationship of the plasma (see p. 222), the formation of fibrin has been mentioned as the essential item in coagulation, and the relation of fibrin to its probable precurs...
-(B) Circumstances Which Retard Coagulation
1. Constantly renewed and close inter-relationship with the lining of healthy blood vessels alone affords the requirements essential for the preservation of the living corpuscles and plasma in their n...
-Coagulation Within The Vessels
Since the blood coagulates spontaneously when removed from the body, the question now arises, How does it remain fluid in the blood vessels? Though this question has long occupied much attention, i...
-Chapter XVI. The Heart
The course taken by the blood in its way to the various parts of the body is called the circulation, on account of its having to make repeatedly the circuit of vessels leading to and from the heart. T...
-The Heart
The heart of man and other warm-blooded animals may be said to be made up of two muscular sacs, the pulmonary and systemic pumps, or, as they are commonly termed, the right and left sides of the heart...
-Arrangement Of Muscle Fibres
At the attachment of each auricle to its corresponding ventricle there is situated a dense ring of tough connective tissue, which surrounds the openings leading from the auricles to the ventricles. Si...
-Minute Structure
The muscle tissue of the heart differs both in structure and mode of action from the other contractile tissues of the body. The elements are firmly united with one another to form irregular close netw...
-Valves
The orifices which lead into and out of the ventricles have peculiar arrangements of their lining texture, forming valves which allow the blood to pass only in a certain direction. These valves, which...
-Action Of The Valves, Auriculo-Ventricular Valves
The mode of action of the flaps of the tricuspid and mitral valves is like that of a lateen sail of a boat, if we substitute the blood stream for the air current; the tendinous cords acting as the sh...
-The Arterial Valves
The semilunar valves are mere membranous pockets, and have no tendinous cords attached to them; but on account of the extent of their convex attachment, when their free margin is made tense by the poc...
-Cardiac Cycle
It is only by means of these valvular arrangements that the heart is enabled to perform its function of pumping the blood in a constant direction onward to empty the veins and fill the arteries. Th...
-Systole Of The Heart
The systole of the corresponding cavities of both sides of the heart is exactly synchronous; that is to say, the two auricles contract simultaneously, and the contraction of the two ventricles follows...
-Cardiac Movements
If the thorax of a recently killed frog be opened, the heart can be observed beating in situ, and the different acts in the cycle studied without difficulty. In mammalians, in order to see the hear...
-Heart's Impulse
The heart communicates its motion to the chest wall, and the movement can be felt and seen over a limited area, which varies with the thinness of the individual. This cardiac impulse, as the stroke is...
-Heart Sounds
The heart's action is accompanied by two distinct sounds, which can be heard by bringing the ear into firm, direct contact with the praecordial region, or indirectly by the use of the stethoscope.* ...
-Innervation Of The Heart
A most interesting phenomenon in the heart's action, and one difficult to explain, is the wonderful regularity of its rhythmical contractions under normal circumstances, and the extreme delicacy of th...
-Intrinsic Nerve Mechanisms
In cold-blooded animals, such as a frog or tortoise, the heart will beat for days after its removal from the animal, if it be protected from injury and prevented from drying. In warmblooded animals th...
-Extrinsic Cardiac Nerves
The intrinsic nerve mechanism of the heart just described is under the immediate control of the great nervous centres through the medium of fibres passing from the medulla oblongata by the vagus and s...
-Inhibitory Nerves Of The Heart
It was observed by Weber (i) that electric stimulation of the vagus nerve caused a slowing of the heart's rhythm, and if increased gave rise to a standstill of the heart in diastole; (2) that the hear...
-The Accelerator Nerves
It has been found that stimulation of the cervical portion of the spinal cord causes quickening of the heart beat. This occurs even after the possibility of increase of blood pressure has been removed...
-Afferent Cardiac Nerves
Besides the nerve channels bearing impulses to the heart, others pass from the heart to the medulla, probably having their origin in the inner lining of the heart, which is the part most sensitive to ...
-Chapter XVII. The Blood Vessels
The channels which carry the blood through the body form a closed system of elastic tubes, which may be divided into three varieties: - 1. Arteries. 2. Capillaries. 3. Veins. The arteries ...
-Arteries
The arteries are those vessels which carry the blood from the heart to the capillaries. The great trunk of the aorta, which springs from the left ventricle, gives off a series of branches, which in tu...
-Capillaries
The frequently branching arterioles finally terminate in the capillaries, in which distinct branches can no longer be recog nized, but the thin canals are interwoven into a network of blood channels, ...
-Veins
The veins arise from the capillary network, commencing as radicles which unite in a way corresponding to the division of the arterioles, but they form wider and more numerous channels. They rapidly co...
-Aggregate Sectional Area Of The Vessels
The general aggregate diameter of the different parts of the vascular system varies greatly. The combined calibre of the branches of an artery exceeds that of the parent trunk, so that the aggregate s...
-Physical Forces Of The Circulation
A liquid flows through a tube as the result of a difference of pressure in the different parts of the tube. The liquid moves from the part where the pressure is higher toward that where it is lower, e...
-Blood Pressure
The cause of the blood's motion is simply a difference in the pressure within the various parts of the vascular system, for the heart acts as the pump filling the tube represented by the large elastic...
-Sustentation Of The Arterial Blood Pressure
The fundamental problem that must be clearly understood in studying the dynamics of the circulation is how the high pressure in the arteries is kept up, or, in other words, how the arteries can exert ...
-Heart Beat
If any factor fail, the mechanism of the circulation is at once impaired. For example, the heart's beat may be stopped by the stimulation of the inhibitory nerve fibres of the vagus, in which case the...
-Measurement Of The Blood Pressure
The first attempt at direct measurement of blood pressure was made by the Rev. Stephen Hales about the middle of the last century, who, wishing to compare the motion of fluids in animals with that in ...
-Variations In The Blood Pressure
If the blood pressure be recorded with Ludwig's Kymograph, a tracing will be obtained which shows that the pressure undergoes periodic elevations and depressions of two different kinds. The smaller os...
-Influence Of Respiration On Blood Pressure
The explanation of the respiratory undulations in the tracing of the blood pressure is difficult. Though many causes have been assigned, no single one appears to explain adequately all the changes tha...
-The Arterial Pulse
Each systole of the ventricle sends a quantity of blood into the aorta, and thus communicates a stroke to the blood in that vessel. The incompressible fluid causes the tense arterial wall to distend s...
-Velocity Of The Blood Current
The velocity of the blood must not be confounded with the velocity of the pulse wave, which bears to it the same relation as the surface waves on a river do to the rate of the stream of water. It h...
-Work Done By The Heart
The amount of work done by any form of engine may be expressed as so many kilogrammetres per hour. That is to say, the numbers of kilogrammes it could raise to the height of one metre in that time. ...
-Controlling Mechanisms Of The Blood Vessels. Vasomotor Nerves
That the arteries possessed elastic resiliency and vital contractility which regulated the amount of blood flowing to any given part was observed by John Hunter in studying inflammation. The muscle...
-Vasomotor Centres
The nerve cells which govern the majority of the vasomotor channels, lie in the upper part of the medulla oblongata in the floor of the fourth ventricle. This is proved by two facts: 1st, most of the ...
-Regulation Of The Distribution Of The Blood
The various experimental results recently obtained on this subject (too numerous to be mentioned here), show that the vascular nerve mechanisms are very complex. The supposition of some such arrangeme...
-Chapter XVIII. The Mechanism Of Respiration
The blood undergoes a series of modifications, and is constantly being altered as it passes from one part or organ to another. It has already been seen that a quantity of nutrient material is taken...
-Respiratory Mechanism In Lower Animals
In the lowest class of animals (e. g., amoeba), we find no special organs for the purpose of respiration, the gas interchange being sufficiently provided for by the exposure of the general surface of ...
-Structure Of The Lung And Air Passages
The respiratory apparatus of mammals consists of (1) vascular sacs filled with air, known as the lung alveoli (2) channels by which these sacs are ventilated - the air passages; (3) motor arra...
-Pleura
The external surface of the lungs is invested by a serous membrane, the pleura, which is reflected to the wall of the thorax from the roots of the lungs, and completely lines the cavity in which they ...
-Respiratory Centres
The normal, rhythmical, coordinated movements of respiration are not only brought about, but are also regulated by an involuntary nervous mechanism. Since we are unconscious of its action, it certainl...
-Excitation Of Respiratory Centre
What keeps this centre active? It has been already stated that all the conditions of the body which cause an increased tissue change, use up a greater amount of oxygen and give off more carbonic acid,...
-Regulation Of Respiratory Activity
Although the respiratory centre is in the common sense automatic, yet it is constantly affected by many influences coming from other parts, which reflexly modify the respiratory movements. Thus mental...
-Modified Movements Of The Respiratory Muscles
Besides the ordinary respiratory motions and the voluntary modifications made use of in speaking, singing, etc., the muscles of respiration perform a series of movements of an involuntary reflex natur...
-Chapter XIX. The Chemistry Of Respiration
The simplest way to investigate the study of the gas interchange that takes place in the lungs, between the air and the blood, is to compare the composition of the expired air with that of the atmosph...
-Expired Air
The following are the notable characters in the tidal air on its leaving the air passages: i. It is rich in C02, containing in quiet breathing on an average 4.38 per cent, instead of.04 per cent. 2...
-Changes The Blood Undergoes In The Lungs
In order to understand how the oxygen and the carbonic acid pass to and from the blood in the pulmonary capillaries we must know the relationship of these gases to the blood in the arterial and venous...
-Internal Respiration
The arterial blood, while flowing through the capillaries of the systemic circulation and supplying the tissues with nutriment, undergoes changes which are called internal or tissue respiration, and w...
-Respiration Of Abnormal Air, Etc
The oxygen income and carbonic acid output are the essential changes brought about by respiration, therefore the presence of oxygen in a certain proportion is absolutely necessary for life. The 21 per...
-Ventilation
In the open air the effects of respiration on the atmosphere cannot be appreciated, but in enclosed spaces, such as houses, rooms, etc., which are occupied by many persons, the air soon becomes apprec...
-Asphyxia
If an adequate supply of oxygen be withheld and its percentage in the blood is reduced to a certain point, the death of the animal follows in three to five minutes, accompanied by a series of phenomen...
-Chapter XX. Blood-Elaborating Glands
In the preceding chapters we have seen that the blood undergoes important changes as it courses through the different parts of its circuit. Where it comes in contact with the tissues it yields to them...
-Ductless Glands
There is a certain set of organs which have but slight traits of resemblance to one another, and in consequence of the want of more accurate knowledge as to their exact function, and the fact that the...
-Supra-Renal Capsule
With regard to the function of the supra-renal capsule we may say that nothing definite is known. The cortical part is said to resemble the lymph follicles in structure, while the central part, on acc...
-Thyroid Body
The thyroid is made up of groups of minute closed sacs embedded in a stroma of connective tissue, lined with a single row of epithelium cells, and filled with a clear fluid containing mucin. In the ad...
-Spleen
Structure The spleen also resembles a lymphatic organ in structure, but differs from it in the relation borne by the blood to the elements of the follicular tissue. It is encased in a strong capsul...
-Extirpation Of The Spleen
The spleen may be removed from the body without any marked changes taking place in the blood or the economy generally. It is said that if an animal whose spleen is extirpated be allowed to live for a ...
-Glycogenic Function Of The Liver
Of all the organs that modify the composition of the blood flowing through them, the liver plays the most important part in elaborating the circulating fluid. The elimination of the various constituen...
-Glycogen
Glycogen is a substance nearly allied to starch in its chemical composition, and is converted with great readiness into grape sugar by the action of certain ferments and acids. Many of the animal text...
-Chapter XXI. Secretions
The secretions which are poured into the alimentary tract have been already described in the chapter on digestion. There are other glands which can now be conveniently considered, since they more or l...
-Surface Glands. Lachrymal Glands
Most vertebrate animals that live in air have a gland in connection with the surface of their eyes, which secretes a thin fluid, to moisten the conjunctiva. This fluid commonly passes from the eye int...
-Mucous Glands
In connection with mouth and stomach secretions, mention has been made of glands which are elongated saccules lined with clear cells with highly refracting contents (Fig. 165). They are distributed ov...
-Sebaceous Glands
These belong to the outer skin, and commonly open into the follicles of the hairs, but also appear on the free surface of the lips and prepuce, etc., where no hairs exist. The secretion cannot be c...
-Mammary Glands
The secretion of milk only takes place under certain circumstances and continues for a limited period. As the name of the glands implies, they are present in all mammalian animals. The activity of the...
-Milk And Its Composition
Milk is a yellowish-white, perfectly opaque, sweetish fluid, with an alkaline reaction and a specific gravity of about 1030. When exposed to the air, particularly in warm weather, the milk soon loses ...
-Excretions
The term excretion is commonly used to denote a gland fluid the,.chief constituents of which are manufactured by other tissues, and are of no use in the economy, but, on the contrary, require to be co...
-Sudoriferous Glands
The sweat glands are distributed all over the cutaneous surface, but in some parts, such as the axilla, perineum, etc., they are both more abundant and larger than elsewhere. They are simple tubes ext...
-Cutaneous Desquamation
Together with cutaneous excretion should be mentioned the continuous and extensive loss all over the surface of the body, from the casting off of the superficial layers, of the dried horny cells of wh...
-Chapter XXII. Urinary Excretion
The urine is the most important fluid excretion, for by it, in mammalia,, nearly all the nitrogen of the used-up proteid leaves the body in the form of urea. The construction of the urinary glands is ...
-Structure Of The Kidneys
The kidneys may be called complex tubular glands, because the tubes of which they are composed are made up of a number of parts essentially differing from one another both in their structure and in th...
-Blood Vessels
The renal artery, on its way from the hilus to the boundary between the cortical and medullary portions of the kidney, breaks up suddenly into numerous small branches; these vessels then form arches, ...
-The Urine
When freshly voided, the urine of man in health is a clear straw-colored fluid, with a peculiar aromatic odor. The intensity of the color varies with the amount of solids - the color being a rough ind...
-Secretion Of The Urine
We have just seen that the arterial twig, or afferent vessel, which enters the capsule of Malpighi, breaks up into a set of capillary loops, which are only covered by a single layer of extremely thin ...
-Chemical Composition Of Urine
The percentage of the solid and liquid materials in urine varies as the secretion alters in strength, but on an average it may be said to contain about 4 per cent, of solids and 96 per cent, water. ...
-Chemical Composition Of Urine. Part 2
Estimation Urea can be estimated volumetrically by the method of Liebig, which depends on the power of mercuric nitrate to give a precipitate with it. The sulphates and phosphates must be first rem...
-Chemical Composition Of Urine. Part 3
Abnormal Constituents Different kinds of substances occur in urine under circumstances of special physiological interest, and therefore may be here enumerated, although their accurate study belongs...
-Nervous Mechanism Of The Urinary Secretion
With regard to the influence exerted by the nervous system on the renal secretion, we have but little satisfactory information, although there can be no doubt that here, as in other glands, the proces...
-Passage Of The Urine To The Bladder
The pressure exerted by the blood in the glomerular capillaries is quite sufficient to make the urine flow from the pelvis of the kidneys into the bladder, because when the ureters are tied they becom...
-Retention Of Urine In The Bladder
The urine, which is continuously secreted and rhythmically conveyed to the bladder, is only voided at convenient times; therefore special arrangements exist for its retention and expulsion. The ret...
-Evacuation Of The Bladder
Micturition, or the expulsion of the urine, does not normally depend on elastic forces alone, as in the case mentioned of paralytic incontinence, when the urine commences to dribble away as soon as a ...
-Chapter XXIII. Nutrition
We can compare the incomings and outgoings of the economy, and should now be in a position to see what light can be thrown by this comparison upon the actual changes which take place in the textures o...
-Tissue Changes In Starvation
As is well known, deprivation of oxygen - by cessation of the respiratory function - almost immediately puts an end to the tissue changes necessary for life, so that the oxygen income cannot be interf...
-Nutritive Equilibrium
The third case mentioned, viz., that in which the nutritive equilibrium is exactly maintained, so that the body weight remains unaltered, is the most important one for us to determine, since its final...
-Nitrogenous Diet
An animal fed upon a purely meat diet requires a great amount of it to sustain its body weight. It has been found that from 1/20 to 1/25 of the body weight in lean meat daily is necessary to keep an a...
-Mixed Diet
The addition of fat or sugar to meat diet allows of a considerable reduction in the supply of meat, both the body weight and nitrogenous tissue change preserving their equilibrium on a smaller amount ...
-Excessive Consumption
The last case we have to consider is that in which the supply of food material is in excess of the requirements of the economy. This is certainly the commonest case in man. Much of the surplus food...
-Chapter XXIV. Animal Heat
The bodies of most animals are considerably warmer than their surroundings. Part of the energy set free by the chemical changes in the animal tissues appears as heat which is devoted to this purpose. ...
-Income And Expenditure Of Heat. Income
The chemical changes which give rise to heat cause a certain waste of the tissues, which have again to be renewed by the assimilation of various nutrient materials. Food is thus the fuel of the animal...
-Temperature Balance
As has been said, the exact income of heat is uncertain and variable, because the data upon which the absolute amount can be calculated are not scientifically free from error. According to the most ca...
-Temperature Balance. Compensation For External Variations Of Temperature
When the temperature of the air rises much above the average, the escape of heat is correspondingly hindered; and when the general body temperature begins to rise by this retention of caloric, we have...
-Chapter XXV. Contractile Tissues
In the lower forms of organisms the motions executed by protoplasm suffice for all their requirements. Thus the amoeba manages to pass through its lifetime with no other kind of motion at its disposal...
-Histology Of Muscle
The term muscle includes the textures in which the protoplasm is specially differentiated for purposes of contraction. The muscle tissues of the higher animals may be divided into two classes: (i) ...
-Properties Of Muscle In The Passive State
Consistence The contractile substance of muscle is so soft as to deserve rather the name fluid than solid; it will not drop as a liquid, but its separate parts will flow together again like half-me...
-Muscle Elasticity
Striated muscle is easily stretched, and, if the extension be not carried too far, recovers very completely its original length. That is to say, the elasticity of muscle is small or weak, but very per...
-Muscle Electric Phenomena
In a living muscle electric currents may be detected, having a definite direction, and certain relations to the vitality of the tissue. As they seem to be invariably present in a passive muscle, they ...
-Active State Of Muscle
A muscle is capable of changing from the passive elongated condition, the properties of which have just been described, into a state of contraction or activity.. Besides the change in form, obvious in...
-Muscle Stimuli
The circumstances which call forth muscle contraction may be enumerated thus: 1. Mechanical Stimulation Any sudden blow, pinch, etc., of a living muscle causes a momentary contraction, which rap...
-Changes Occurring In Muscle On Its Entering The Active State
Changes In Structure The examination of muscle with the microscope during its contraction is attended with considerable difficulty, and in the higher animals has not led to satisfactory results. In...
-Changes Occurring In Muscle On Its Entering The Active State. Continued
Rheoscopic Erog The negative variation of a single contraction can be easily shown on the sensitive animal tissues. For this purpose the sciatic nerve of a frog's leg is placed upon the surface of ...
-The Graphic Method Of Recording Muscle Contraction
In order to study the details of the contraction of muscle, the graphic method of recording the motion is applied. The curve may be drawn on an ordinary cylinder moving sufficiently rapidly. Where acc...
-Single Contraction
In response to an instantaneous stimulus, such as occurs in the secondary coil on breaking the primary current, a muscle gives a momentary twitch or spasm, commonly spoken of as a single contraction, ...
-Single Contraction. Continued
The greatest difference is observed in the muscles found in different kinds of animals. The contraction of some kinds of muscle tissue (non-striated muscle of mollusca, for example) occupies several m...
-Tetanus
If a series of stimuli be applied in succession, at intervals less than the duration of a single contraction, a summation of con tractions occurs, which results in the accumulation of effect until the...
-Muscle Tone
Although the tracing drawn by a lever attached to a muscle in tetanus is straight, and does not show any variation in the tension of the tetanized muscle, some variations in tension must occur, since ...
-Muscle Irritability And Fatigue
The activity of the muscle tissue of mammalian animals is closely dependent upon a good supply of nutrition, and if its blood current be completely cut off by any means for a length of time, it loses ...
-Death Rigor
The death of muscle tissue is associated with a set of changes which, in some respects, resemble those observed in its active state. The most obvious phenomenon is an unyielding contraction, which cau...
-Unstriated Muscle
So far reference has only been made to the skeletal muscles, the fibres of which are marked by transverse striations, and whose single contraction is extremely rapid and short. The contractile tissues...
-Chapter XXVI. The Application Of Skeletal Muscles
The consideration of the many varieties of muscles, and the various modes in which they are attached to the bones that they are destined to move, belongs to the department of practical anatomy, and ne...
-Joints
The unions between the bones of the skeleton are very varied in function and character. They may be classed as: i. Sutures, in which the bones are firmly united by rugged surfaces without the interpos...
-Standing
In order that an elongated rigid body may stand upright, it is only necessary that a line drawn vertically through its centre of gravity should pass within its basis of support, and, if the latter be ...
-Walking And Running
Walking is accomplished by poising the weight on one foot and then tilting the body forward with the other, which is then swung in front and placed on the ground to prevent falling. These acts are per...
-Chapter XXVII. Voice And Speech
The human voice is produced by an expiratory blast of air being forced through the narrow opening at the top of the windpipe, called the glottis. This glottis, which lies in the lower part of the lary...
-Mechanism Of Vocalization. Shape Of The Opening Of The Glottis
Taking the thyroid cartilage as the fixed base, the cricoid and arytenoid cartilages undergo movements which bring about two distinct sets of changes in the glottis and its elastic edges, namely, (1) ...
-Properties Of The Human Voice
In the voice we can recognize the properties noted in other kinds of sound. These are quality, pitch and intensity. 1. The quality of vocal sound is almost endless in variety, as is shown by the vo...
-Nervous Mechanism Of Voice
The nervous mechanism, by means of which vocal sounds are produced, is among the most complexly coordinated actions that regulate muscular movements. Like respiration, vocalization at first seems a...
-Speech
The variations in vocal sounds which give rise to speech are not produced in the larynx, but in the throat, mouth and nose. When unaccompanied by any vocal sound, speech only gives rise to a whisper; ...
-Chapter XXVIII. General Physiology Of The Nervous System
Anatomical Sketch The nervous system includes the various mechanisms by which the distant parts of the body are kept in functional relationship with one another. By it the condition of the surround...
-The Active State Of Nerve Fibres
Nerves pass into a state of activity in response to a variety of stimuli, but their active condition cannot be readily recognized, because the only change we can detect in the nerve is that which take...
-Velocity Of Nerve Force
It has already been stated that nerve fibres are capable of conducting impulses in either direction - from or to the nervous centres. The position and character of the terminal organs determines the d...
-The Electric Change In Nerve. Negative Variation
The natural current of a nerve, like that of muscle, undergoes a diminution at the moment the nerve is stimulated; this is termed the negative variation. It occurs with any other form of stimulation a...
-Electrotonus
If one of two wires leading to a galvanometer be applied to the centre, and the other to the end of a nerve, so as to indicate the natural current, and at the same time another part of the nerve be pl...
-Irritability Of Nerve Fibres
The irritability of nerves varies according to certain conditions and circumstances. While uninjured in the body, the irritability of a nerve depends upon - 1. A supply of blood sufficient to suppl...
-The Law Of Nerve Contraction
Upon the foregoing facts, and others already mentioned - viz., that the impulse starts in the nerve from different poles and with different force, with a making and a breaking shock - depends the law ...
-Nerve Corpuscles Or Terminals
These are the real actors in the nerve operations, while the fibres are merely their means of communicating with one another. One set of terminals is placed on the surface of the body and is adapted t...
-The Functions Of Nerve Cells
Any mass of living protoplasm, such as an amoeba, can receive extrinsic stimuli, which affect directly its conditions, and though the impression may be very localized in its application, yet all the p...
-Chapter XXIX. Special Physiology Of Nerves. Spinal Nerves
The thirty-one pairs of nerves which leave the vertebral canal by the openings between the vertebrae are called spinal nerves, in contradistinction to the cranial nerves, which pass through the base o...
-Posterior Roots
The fact that when the leg on the side where the anterior roots have been severed is stimulated the animal moves the other, is sufficient to show that the sensory connections between its surface and t...
-Recurrent Fibres
It has been sometimes found that stimulation of the anterior roots seemed to cause pain, as shown by the motion of other parts besides those to which this root was distributed; and it was believed tha...
-The Cranial Nerves
The nerves which pass out through the foramina in the base of the skull must be considered separately, as the function of each of them shows some peculiarity. Some are exclusively nerves of special se...
-III. The Motor Oculi Nerve
The nerves of the third pair are efferent, being the chief motor nerves of the eyes. They arise from the gray matter on the floor and roof of the aqueduct of Sylvius, pass out of the brain substance n...
-IV. The Trochlear Nerve
This thin nervous filament arises under the Sylvian aqueduct, and passes into the superior oblique muscle, to which it carries voluntary impulses, which are involuntarily associated with those of the ...
-VI. The Abductor Nerve Of The Eye
This arises in the floor of the fourth ventricle, and appears just below the pons Varolii. It is the motor nerve of the external rectus muscle of the eye. Paralysis or section of it causes inward squi...
-VII. (Portio Dura)^ Motor Nerve Of The Face
This nerve arises from a gray nucleus in the floor of the fourth ventricle. It passes, with the other part of the seventh (portio mollis) or auditory nerve, into the internal auditory meatus of the te...
-V. N. Trigeminus, Or Trifacial Nerve
This nerve transmits both efferent and afferent impulses carried by two different strands of fibres. The motor part, which arises from a gray nucleus in the floor of the fourth ventricle, is much the ...
-The Ciliary Or Ophthalmic Ganglion
This ganglion lies in the orbit. It has three roots, which come from - (1) the inferior oblique branch of the third nerve, by a short slip, which forms the motor root; (2) from the nasal branch of the...
-The Sphenopalatine Or Nasal Ganglion
This lies on the second division of the fifth nerve, from which it gets its sensory root. Its motor root comes from the seventh by the great superficial petrosal nerve, and its sympathetic root from t...
-Otic Or Ear Ganglion
The otic ganglion lies under the foramen ovale, where the interior division of the fifth comes from the cranium. Its roots are - (1) motor; (2) sensory, from the inferior division of the fifth; and (3...
-The Submaxillary Ganglion
This is on the hyoglossus muscle in close relation to the lingual branch of the fifth, from which it gets a sensory root. The chorda tympani passes to the ganglion, carrying efferent impulses through ...
-VIII. The Glosso-Pharyngeal Nerve
This nerve forms part of the eighth pair, and springs from the floor of the fourth ventricle above the nucleus of the vagus. It is a mixed nerve, the functions of which may be thus classified: - Af...
-The Spinal Accessory Nerves
These also form part of the eighth pair of nerves, and arise from the medulla oblongata and spinal cord, as low down as the seventh cervical vertebra. The lower fibres leave the lateral columns at the...
-The Vagus Nerve
The vagus arises from the lower part of the floor of the fourth ventricle, and is connected with many of the important groups of nerve cells in this neighborhood. The functions of its widely-distri...
-IX. Hypoglossal Nerve
This nerve appears in the furrow between the olivary body and the anterior pyramid, on a line with the anterior roots of the spinal nerves. It corresponds with the anterior roots in function, being a ...
-Chapter XXX. Special Senses
It has been pointed out that the afferent or sensory nerves receive impressions at the surface of the body, and carry the impulses to nerve cells in the brain, where they give rise to sensation. The a...
-Skin Sensations
The sensations arising from many impulses coming from the skin are grouped together under the name of the Sense of Touch. This special sense may be resolved into a number of specific sensations, each ...
-Nerve Endings
Although the end organs of the nerves of the skin are the simplest of all those belonging to the apparatus of special sense, yet we have a very imperfect knowledge of their immediate relationships to ...
-Sense Of Locality
By this is meant our power of judging the exact position of any point or points of contact which may be applied to the skin. Thus, if the point of a pin be gently laid on a sensitive part of the skin ...
-The Sense Of Pressure
There seems to be a reason for separating the perception of differences in the degree of pressure exercised by a body from the simple tactile or local impression. If we support a part of the body so t...
-Temperature Sense
We are able to judge of the difference in temperature of bodies which come in contact with our skin. Since our sensations have no accurate standard for comparison, we are unable to form any exact conc...
-General Sensations
We call general sensations those feelings, pleasurable or otherwise, which can be excited without our being able to refer them to external objects, compare their sensation with those of the special se...
-Sense Of Taste
Next to the sense of touch, which is unevenly distributed over the whole cutaneous surface, taste is anatomically the least accurately localized. Though confined to the mouth, its more accurate limita...
-Sense Of Smell
The numerous delicate nerves which pass from the olfactory bulb to the mucous membrane of the upper and part of the middle meatus of the nose form the special nerves of smell. When certain subtle part...
-Chapter XXXII. Vision
Next in importance to those impulses which we receive from the skin are those conveyed to the brain from the outer world by the second pair of cranial, or the optic nerves. The ending of the optic ...
-The Tunics Of The Eyeball
The organ of vision of vertebrate animals is enclosed in a firm case of fibrous tissues called the sclerotic coat, which is continuous with the sheath of the optic nerve. It is seen between the eyelid...
-The Dioptric Media Of The Eyeball
The transparent substances which fill the eyeball are, together with the cornea, called the dioptric media. The aqueous humor lies in contact with the posterior surface of the cornea, and just fills t...
-Dioptrics Of The Eye
Light travels through any even transparent body, such as the atmosphere, in a straight line. But when it meets any change in density, particularly when it has to pass obliquely into a denser medium, t...
-Three Media And Refracting Surfaces
Since the surfaces of the cornea, however, are practically parallel, we may neglect the difference between it and the aqueous humor, and look upon the two as one medium, having in front the shape of t...
-Scheiner's Experiment
It may be seen from the foregoing figure that if the retina, which normally would lie at 2, were placed nearer the dioptric apparatus, say at 1, or further from it, at 3, it would not meet the exact p...
-Accommodation
The difference of distance for which we can adjust our eyes is great, so that our range of distinct vision is very extensive. As already stated, the normal eye is considered to be constructed so that ...
-Muscular Mechanism Of Accommodation
The alteration in the shape of the lens is accomplished by the action of the muscular layer, already named, which radiates from the edge of the cornea to the ciliary region of the choroid coat, where ...
-Defects Of Accommodation. Myopia
It has been said that*the near limit of distinct vision differs in many persons from the twelve centimeters of the normal emmetropic eye, and it is found that the power of accommodation varies very ...
-Hypermetropia
Another abnormality is long sight. In the hypermetropic eye, parallel rays of light are brought to a focus at a point beyond the retina, so that divergent or parallel rays cause diffusion circles an...
-Defects Of Dioptric Apparatus
In common with all dioptric instruments the eye has certain optical defects which tend to interfere with the distinctness of the image. Chromatic aberration is due to the breaking up of white light...
-The Iris. Functions
It has already been mentioned that the motions of the iris alter the size of the pupillary aperture through which the rays of light must pass, and while it regulates the amount of light admitted, it a...
-Nervous Mechanisms Controlling The Iris
When the sympathetic in the neck is cut, the pupil becomes considerably contracted. Hence, it has been argued that the nerves supplying the dilator are derived from the sympathetic. These fibres ar...
-The Ophthalmoscope
When we look into the eye the pupil appears quite black, no matter in what position we place the light. The reason of this is that the retina can only be made visible by the light reflected outward fr...
-Light Impressions
The retina is that part of the eye by which the physical motions called light are changed into what are known physiologically as nerve impulses, by means of which the impression of light is excited in...
-The Function Of The Retina
The retina is a complex peripheral nervous mechanism composed of many elements, the special functions of which are not adequately known. It spreads over the fundus of the eye, but where the nerve pier...
-Retinal Stimulation. Point Of Greatest Sensitiveness
As in the perception of two points of contact with the skin, so we find the retina ceases to be able to distinguish the difference between two luminous points, if they be brought to a focus at a dista...
-Excitation Of Nerve Impulse
The question now arises, How do the retinae, or rather their outer layers, convert light into a nerve stimulus? It would appear quite out of the question that the 394 to 760 billions of waves of light...
-Color Perceptions
If a beam of white sunlight be allowed to pass through an angular piece of glass it is decomposed into a number of colors which may be seen by looking through the prism, or may be thrown on a screen, ...
-Mental Operations In Vision
Our visual sensations enable us to perceive the existence, position and correct form of the various objects around us. For visual perception much more is necessary than the mere perfection of the diop...
-Movements Of The Eyeballs
The eyeballs may be regarded as spherical bodies, lying in loosely fitted sockets of connective tissue padded with fat, in which they can move or revolve freely in all directions, in a limited degree....
-Binocular Vision
When we look at an object with both eyes we have a separate image thrown upon each retina, and therefore two sets of impulses are sent to the sensorium, one from the right and one from the left eye. Y...
-Chapter XXXIII. Hearing
Just as impulses traveling along the optic nerves can only give rise, in the sensorium, to impressions of light, so impulses passing to the sensorium via the auditory part of the portio mollis of the ...
-Conduction Of Sound Vibrations Through The External Ear
External Ear In man, the muscles are so poorly developed that he can hardly move the external ear or pinna perceptibly, and the part commonly called the ear is of little use. We know this, because ...
-Conduction Of Sound Vibrations Through The Tympanum
The end of the auditory canal is closed by the membrana tym-pani, which slopes obliquely from above downward and inward, in which direction its size is greater than if it were straight across the cana...
-Eustachian Tube
The tympanum is connected with the pharynx by means of the Eustachian tube, which, though habitually closed, is opened for a moment by swallowing and other motions of the pharynx. On these occasions a...
-Sound Conduction Through The Labyrinth
Every motion of the oval base of the stapes causes a wave to pass along the liquid in the labyrinth. The bony case of the internal ear being firm, the wave travels through all parts of the internal ea...
-Terminals Of The Auditory Nerve
The nervous mechanisms which are most important for the appreciation of tones are those situated in the cochlea. The nerve endings found in the membranous sacs in the vestibule are connected with p...
-Stimulation Of The Auditory Nerve
The stimulation of the nerve of hearing by sound vibrations of the air is less difficult to understand than the excitation of the optic nerve by light waves which are conveyed by an imponderable mediu...
-Chapter XXXIV. Central Nervous Organs
The central part of the nervous system, or cerebro-spinal axis, consists of the spinal cord, the medulla oblongata and the brain. The central nervous organs are composed of a soft texture, consisti...
-The Spinal Cord
The spinal cord, being the great bond of connection between the brain and the majority of the peripheral nerves, is necessarily a conducting apparatus of the very first importance, and from the quanti...
-The Spinal Cord. Continued
2. The crossed or lateral pyramidal tracts (Fig. 246, P) are continuous with the pyramids of the opposite side of the medulla where the crossing of the fibres is completed. They lie in the lateral whi...
-Spinal Cord As A Collection Of Nerve Centres
In the gray substance there is still greater difficulty in tracing the course taken by the various kinds of impulses, and little is known on the subject beyond what is surmised from the proximity of t...
-Reflex Action
When an afferent impulse arrives at the cells of the posterior column, it is communicated to the cells in the same segment, and reaching motor cells it gives rise to a movement of the muscles of the n...
-Strength And Duration Of Stimulus
By graduating the strength of the acid used to moisten a square millimetre of blotting paper, the following results are obtained: When very weak acid is employed only slight local and unilateral movem...
-Exalted Excitability Of The Cells
In certain conditions of the nervous system convulsions can be readily excited. As most striking among these, may be named poisoning with the alkaloid of nux vomica (strychnia), and the state of the b...
-Inhibition Of Reflex Action
The great majority of reflex actions may be prevented or controlled by the will, and the basal ganglia and medulla habitually exert a checking or inhibitory influence on the reflex actions of the spin...
-Special Reflex Centres
Many of the groups of nerve cells in the cord are employed in executing familiar acts essential to the animal economy independent of the will. Many of these acts are very complex, and require the coor...
-Coordination
From what has been said concerning the more complex reflex actions, it is clear that the cells of the spinal cord are capable of arranging the discharge of nerve impulses, so as to bring about definit...
-Automatism
Resides being excited to action by impulses coming from the brain - volition - and from the surface - reflexion - the groups of cells in the spinal cord may act without any obvious incoming impulse; t...
-Chapter XXXV. The Medulla Oblongata
The direct continuation of the spinal cord is called the medulla oblongata. It consists of representatives of the various parts of the cord, with some additional gray matter. The relationship of the d...
-The Medulla Oblongata As A Central Organ
A number of groups of ganglion cells with special duties are located in the medulla. Those acts which are most important for the execution of the vegetative functions, are arranged and governed by the...
-Respiratory Centre
The centre which regulates the respiratory movements is situated in the floor of the fourth ventricle, at the upper and back part of the medulla. Flourens long since showed that injury of this spot - ...
-The Vasomotor Centre
It has already been stated that groups of cells exist in the gray part of the spinal cord, which, according to the class of animal, have more or less direct influence upon the muscles in the coats of ...
-The Cardiac Centre
Although the heart beats periodically when cut off from the nervous centres, its normal rhythm is under the control of a group of nerve cells in the medulla, from which some fibres of the vagus carry ...
-Chapter XXXVI. The Brain
As we pass upward in attempting to trace the conducting channels of the medulla, we come to the more elaborate system of nervous textures which, together, are called the brain. This is anatomically th...
-The Mesencephalon And Cerebellum
In examining the functions of the brain, we may consider the various parts in the order they are found in proceeding from the medulla toward the cerebral hemispheres. Between the medulla oblongata and...
-Crura Cerebri
Passing above the Pons Varolii, we come to an isthmus, composed of two thick strands of nerve substance connecting the pons Varolii with the cerebral hemispheres. These are called the crura cerebri. T...
-Basal Ganglia
On the floor of the lateral ventricles are the corpora striata and optic thalami, which together are spoken of as the basal ganglia. The exact relationship borne by their functions to those of the mes...
-Corpora Striata
The motor tracts, coming from below, lie in the lower part of the crus cerebri, and thence one on each side passes into the corresponding corpus striatum. Anatomically, this part may be regarded as th...
-Optic Thalami
The evidence concerning the function of these ganglionic masses is far from being even as satisfactory or conclusive as that relating to the corpora striata. Anatomically, their relationship is equ...
-Cerebral Hemispheres
It is now universally regarded as a recognized fact that the hemispheres of the brain are the seat of the mental faculties perception, memory, thought and volition. The cerebral cortex is the part of ...
-Localization Of The Cerebral Functions
Whether the entire surface of the hemispheres can be mapped out into areas, each of which is set apart for a definite immutable function, is a question surrounded with difficulty, and which, up to the...
-Chapter XXXVII. Reproduction. Male And Female Generative Elements
One of the chief characteristics of living beings is their power of reproduction; that is to say, organisms can, under favorable conditions, form other individuals with lives and habits similar to the...
-Menstruation And Ovulation
After puberty, at intervals averaging about four weeks, the genital organs of the female become congested, and at the same time a Graafian follicle is ruptured and its contained ovum set free. Coincid...
-Changes In The Ovum Subsequent To Impregnation
The first changes in the ovum independent of impregnation consist in the shrinking of the yolk from the vitelline membrane, and the extrusion from it of certain granular bodies which lie between it an...
-Formation Of The Membranes. (1) The Amnion
The mesoblast around the embryo becomes thickened, and is split into two distinct layers; this cleavage is at first confined to the neighborhood of the embryo, but gradually spreads over the whole bla...
-(2) The Yolk Sac
The Yolk Sac is that part of the blastoderm which grows and envelops the yolk, which previously was only surrounded by the vitelline membrane. After the mesoblast has split into two layers, the splanc...
-(3) The Allantois
The Allantois, or urinary vesicle, in the chick is of importance, as the vessels developed in it are used for respiratory purposes, being spread out beneath the porous shell. In the mammalian embryo i...
-(4) The Chorion
The Chorion is the external covering of the ovum. At first it consists simply of the zona pellucida or vitelline membrane, and then it is called the primitive chorion. Later it is supplemented by that...
-The Placenta
The Placenta is an organ most important to the mammalian embryo. It conveys not only nourishment but also oxygen from the maternal blood to that of the foetus. It is, of course, necessary that the ani...
-Relation Of The Foetal To Maternal Placenta
The maternal part is formed from the decidua serotina, which becomes much thickened and very vascular where the placenta is attached. The fcetal placenta is derived from the chorion, which sends out a...
-Chapter XXXVIII. Development Of The Special Systems. Development Of The Vertebral Axis
The earliest evidence of the differentiation of the blastoderm consists in the appearance of the primitive streak which forms the first sign of the embryo. This is a line which appears near what is to...
-Development Of The Central Nervous System. Spinal Cord
Soon after the closure of the medullary or neural canal at its anterior or cranial end, it is dilated in this region into three vesicles, known as the first, second, and third cerebral vesicles, from ...
-The Brain. Anterior Cerebral Vesicle
As already mentioned, the brain is formed from the primitive neural canal, the anterior part of which dilates into three little swellings called the anterior, middle and posterior cerebral vesicles. F...
-Middle Cerebral Vesicle
By the cranial flexure the brain is bent at the junction of the first and second cerebral vesicles; Fig. 289. Chick on the third day, seen from beneath as a transparent object, the head being t...
-Posterior Cerebral Vesicle
This is divided into an anterior and a posterior part. From the roof of the anterior division arises the cerebellum, and from its floor the pons Varolii. The posterior division gives rise to the me...
-The Alimentary Canal And Its Appendages
When the blastoderm is bent at its anterior extremity to form the cephalic fold, it closes and forms the anterior boundary of a short canal, the upper wall of which is formed by the general blastoderm...
-Genito-Urinary Apparatus
In the interval between the protovertebrse and the cleavage of the mesoblast into its somatopleural and splanchnopleural layers, a mass of cells arranges itself into a longitudinal ridge. This ridge, ...
-Blood-Vascular System
In the mammalian embryo this may be appropriately divided into two systems of different dates; the first, or early circulation, which is confined to the yolk sac; and the second, or later circulation,...
-Development Of The Heart In The Human Embryo, From The Fourth To The Sixth Week
A. Embryo of four weeks. (Kollfker after Coste). B. Anterior, and C. posterior views of the heart of an embryo of six weeks. (K'olliker after Ecker.) 1. Upper limit of buccal cavity, c. Buccal cavi...
-The Arterial System
Around the pharynx are developed five pairs of aortic arches. These commence anteriorly from the two primitive aortae, and, passing along the side of the pharynx, end in the aortae as they descend to ...
-Venous System
The blood is returned from the head by the two primitive jugulars, which unite with the cardinal veins conveying the blood from the trunk and lower extremities to form a vessel on each side, called th...
-Foetal Circulation
The course taken by the blood through the heart and vessels of the embryo differs essentially from that which persists in adult life. Tracing the blood from the placenta, it passes along the umbili...
-Development Of The Eye
The optic vesicles arise from the anterior cerebral vesicle at a very early period, and their cavities are continuous with that of the fore-brain. With the development of the rudimentary cere-61 bral ...
-Development Of The Ear
The ear is developed chiefly from the epiblast, a special and independent involution of which forms both its essential nervous structures and the general epithelium lining the membranous labyrinth. Th...
-Development Of The Skull And Face
The bones of the roof of the skull and of the face are chiefly derived from membrane, those of the base of the skull being laid down in cartilage. At the cephalic extremity of the notochord is a ma...
-Physiology Glossary
Abscissa The line forming the basis of measurement of graphic records, along which the time measurement is usually made. Accommodation Focusing the eye for different distances; it is effected...
-Physiology Glossary. Part 2
Cathode The negative pole or electrode - i. e., the pole by which the electric current leaves. Cellulose The substance of which vegetable cell walls are formed. Centrifugal Efferent. ...
-Physiology Glossary. Part 3
Impulses which, reflexly, call forth motion. Excito-Secretory Impulses calling forth the activity of gland cells, commonly applied to afferent influences which act reflexly. Fibrinogen A f...
-Physiology Glossary. Part 4
Menstruation The monthly change in the mucous membrane of the uterus, which accompanies the discharge of the ovum. Meroblastic The form of ova in which the yolk does not undergo complete segm...
-Physiology Glossary. Part 5
Protovertebrae The primitive segments of the mesoblast in the site of the future verlebral column. Protozoa That division of the protista which has been assigned to the animal kingdom. Pro...
-A New Series Of Students' Manuals
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-A New Series Of Students' Manuals. Continued
No. 6. Diseases of Children A Manual. By J; F. Goodhart, m.d., Phys. to the Evelina Hospital for Children; Asst. Phys. to Guy's Hospital, London. American Edition. Edited by Louis Starr, m.d., Clin...
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Fillebrown. Operative Dentistry. 330 Illustrations. Just Ready. Cloth, 2.50 Flagg's Plastics and Plastic Filling. 3d Ed. Preparing. Gorgas. Dental Medicine. A Manual of Materia Medica and Therap...
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Cleaveland's Pocket Medical Lexicon. Thirty-first Edition. Giving correct Pronunciation and Definition of Terms used in Medicine and the Collateral Sciences. Very small pocket size. Cloth, red e...
-Eye Books
Arlt. Diseases of the Eye. Including those of the Conjunctiva, Cornea, Sclerotic, Iris and Ciliary Body. By Prof. Von Arlt. Translated by Dr. Lyman Ware. Illus. 8vo. Cloth, 2.50 Hartridge on Refrac...
-Materia Medica And Therapeutics Books
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Byford. Diseases of Women. The Practice of Medicine and Surgery, as applied to the Diseases and Accidents Incident to Women. By W. H. Byford, A .m., m.d., Professor of Gynaecology in Rush Medical Coll...
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Bowlby. Surgical Pathology and Morbid Anatomy, foi Students. 135 Illustrations. 12 mo. Cloth, 2.0c. Davis' Elementary Biology. Illustrated. Cloth, 4.0c. Rindfieisch's General Pathology. By Prof....
-Physiology Books
Yeo's Physiology. Third Edition. The most Popular Students' Book. By Gerald F. Yeo, m.d., f.r.c.s., Professor of Physiology in King's College, London. Small Octavo. 758 pages. 321 carefully printed Il...
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Wythe's Dose and Symptom Book. Containing the Doses and Uses of all the principal Articles of the Materia Medica, etc. Seventeenth Edition. Completely Revised and Rewritten. Just Ready. 32mo. Cloth, 1...
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Anderson, (McCall) Skin Diseases. A complete Text-Book, with Colored Plates and numerous Wood Engravings. 8vo. Just Ready. Cloth, 4.50; Leather, 5.50 We welcome Dr. Anderson's work not only as a f...
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Jacobson. Operations in Surgery. A Systematic Handbook for Physicians, Students and Hospital Surgeons. By W. H. A. Jacobson, b.a., Oxon. f.r.c.s. Eng.; Ass't Surgeon Guy's Hospital ; Surgeon at Royal ...
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Mackenzie. Diseases of the (Esophagus, Nose and Nasopharynx. By Sir Morell Mackenzie, m.d., Senior Physician to the Hospital for Diseases of the Chest and Throat; Lecturer on Diseases of the Throat at...
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Acton. The Reproductive Organs. In Childhood, Youth, Adult Life and Old Age. Seventh Edition. Cloth, 2.00 Beale. Urinary and Renal Diseases and Calculous Disorders. Hints on Diagnosis and Treatment...









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