Animal anatomy was scantily and almost exclusively studied by the ancients; human anatomy was fairly commenced by the Italian schools of the 14th, loth, and 16th centuries; the descriptive branch was chiefly cultivated throughout Europe until the end of the 18th, when Bichat instituted and almost originated the systematic study of general anatomy. Microscopic observations had been made by Malpighi and other anatomists, but many of the great discoveries of comparative and general anatomy have been made in the present age; and the systematic study and development of minute anatomy date from the improved construction of the compound microscope in 1832, before which time it was impossible to make much progress in this most important branch of science. Descriptive or special anatomy is limited to the study of the parts which form the body of one type or individual, or of the two sexes of one species, as man and woman. It does not, however, exclude reference to age and difference of race. - The organs of the body have been classed in various ways by different anatomists, and mostly according to the nature of their special structure and peculiarity of use or function. Bichat's method, slightly modified, is most in use, and is perhaps the best.

By this the organs are classed as follows: I. Organs pertaining to the animal, voluntary, or relational functions.

II. Organs pertaining to the nutritive functions.

III. Organs pertaining to generation, or the reproductive functions. To the first class belong the organs of locomotion, innervation, voice, and sensation. 1st. The skeleton, composed of bones, cartilages, ligaments, and joints, as instruments of locomotion and forming the subject of what is termed osteology. 2d. The muscular system, composed of muscles, tendons, sheaths, and their appendages, as agents of locomotion, forming the subject of myology. 3d. The nervous system, composed of medullary white substance and gray vesicular matter, enclosed in sheaths of serous and fibrous membrane, forming the brain, spinal cord, ganglia, and nerves. The special study of the structure and functions of the nervous system and appendages is termed neurology. 4th. The vocal organs, as an apparatus of relational use between man and the external world, are the larynx or throat, and the mouth; the one as an organ of the voice, and the other as an organ of articulation or speech. 5th. The special organs of sense are distinguished into proper and common; taste, smell, sight, and hearing belong to the former, and touch, the sense of temperature, and the muscular sense of resistance, weight, lassitude, etc, belong to the latter.

The mouth, the nose, the eyes, and the ears are special organs, but the whole external surface of the body serves for the sense of touch and temperature, while the whole internal muscular structure seems to be affected by the sense of lassitude, and the muscular parts of the trunk and limbs are affected by the sense of resistance to external weight or force. - To the second class of organs, pertaining to the functions of nutrition, belong the organs of digestion, respiration, circulation, secretion, and excretion. 1st. The digestive system consists of the alimentary canal, together with its accessory organs, such as the salivary glands, the liver, and the pancreas. The alimentary canal, consisting of its successive portions, namely, the mouth, oesophagus, stomach, small intestine, and large intestine, receives the food and accomplishes its digestion by the mechanical operation of the teeth in mastication, followed by the modifying action of the various digestive secretions. 2d. The heart is the centre of the circulatory system, which consists of two distinct circuits, called pulmonary and systemic.

From the right ventricle of the heart the dark impure blood is sent through the pulmonary arteries into the lungs, where the minute capillary blood vessels are exposed to the almost direct contact of the air, from which oxygen is absorbed to vivify the blood, giving it a bright scarlet red. A thin membrane intervenes between the air in the lungs and the blood, but this does not impede the absorption of oxygen and the exhalation of carbonic acid gas, the one to give new life and the other to rid the blood of poisonous gas and effete matter. When thus purified and renovated in the lungs, the blood returns to the left side of the heart, performing a complete circuit in the region of the heart and lungs alone, for this sole purpose. It is then propelled from the left ventricle of the heart, through the aorta and all the arteries of the whole body, into every organ, for the purpose of nutrition. The capillary vessels ramify minutcly in every organ, and the tissues of the part absorb the nutrient portions of the fluid, and return waste matter to the veins, in exchange for the nutriment brought to them by the arteries.

The general system of arteries carries pure blood to all parts of the body, and the general system of veins returns impure blood from all parts of the body back into the heart, to be thence sent into the lungs for purification, and thus keep up perpetual circulation and renovation, 3d. The respiratory organs are the larynx, the trachea or windpipe, the bronchial tubes, and air vesicles within the lungs. Their function is to breathe in new suit-plies of air to vivify the blood, and to exhale carbonic acid and other vitiated matters, which are poisonous when accumulated in too large a quantity. 4th. The kidneys separate from the blood the elements of the urine, and thus rid the system of another kind of waste matter, which also becomes poisonous if allowed to accumulate within the vessels that contain and circulate the vital fluid. When in the bladder the urine is not dangerous, because no longer mingled with the blood, unless too much accumulated and too long retained. - To the third class of organs belong the reproductive systems, male and female. These are not essential to the life of the individual, as they may be extirpated without danger even to the health. - General anatomy treats of the different sorts of tissue composing the organs of the body.