The diseases of the brain are considered as embracing, in addition to the affections seated in the cerebral substance, or brain proper, those of the investing membranes or the meninges. The meningeal affections, that is, affections seated in the membranes, generally give rise to more or less disturbance of the functions of the brain, and not infrequently the disease extends from the meninges to the cerebral substance. So, also, affections seated primarily in the brain proper often involve secondarily the investing membranes. Again, there are some diseases in which the cerebral'substance and the meninges are simultaneously affected. Considering the diseases of the brain in this comprehensive sense, a convenient classification of them is the following: 1, cerebral congestion; 2, cerebral anaemia; 3, cerebral haemorrhage; 4, inflammatory affections; 5, structural lesions; 6, functional disorders. I. Cerebeal Congestion. Here, as in other parts of the body, the name congestion denotes an overplus of blood (hy-peraemia), which is the result, on the one hand, of an undue detention of blood, the quantity, sent to the part being not necessarily greater, and perhaps even less than in health, or, on the other hand, of an undue supply of blood.

An overplus of blood from detention is distinguished as passive congestion, and the term active congestion denotes an undue determination or supply of blood. In passive congestion the morbid accumulation is chiefly in the returning vessels or veins; in active congestion, the excess of blood is in the distributing vessels or arteries. In either form of congestion, the vessels of both the brain substance and the meninges are abnormally filled with blood. Active congestion of the brain may be caused by undue excitation of the emotional faculties of the mind. "When this is the cause, the excessive functional activity of the brain attracts to the head an undue quantity of arterial blood. Another cause is the abuse of alcoholic stimulants. Here, too, the exciting effect of alcohol upon the brain occasions a morbid afflux to the head. An increase of the muscular walls of the left ventricle of the heart is another cause of active congestion. This is apt to be a cause when the morbid muscular growth (hypertrophy) is not compensated for by certain valvular lesions which obviate this effect. The active congestion under these circumstances is due to the blood being sent to the head in larger quantity and with greater force than in health.

Active congestion of the brain, as regards its degree, varies from an amount which constitutes only a slight malady to an excessive determination of blood leading rapidly, or even suddenly, to death. Existing in a slight or moderate degree, it gives rise to diffused pain in the head, flushing of the face, and deficient or disturbed sleep. In a more marked degree, the headache is intense and accompanied with a sense of bursting, weight, or fulness; the surface of the head is hot; the face is deeply reddened; the vessels of the eyes are injected; the arteries of the temple and neck pulsate strongly, and there is inability to sleep. Active or maniacal delirium is sometimes due to active congestion. Epileptiform convulsions are also, in some cases, attributed to this condition.' A suddenly induced active congestion is among the different conditions giving rise to an apoplectic seizure which may prove speedily fatal. Apoplexy thus induced is distinguished as congestive apoplexy. The congestion may lead gradually to loss of consciousness, or coma, which may end in death. In some of the cases of insolation, or sunstroke, the only pathological condition found after death is cerebral congestion. - Active congestion of the brain may be diminished and often removed by appropriate treatment.

If dependent on mental excitement or the abuse of alcohol, the continued operation of these causes is of course, if possible, to be prevented. In the rare cases of simple hypertrophy of the heart, that is, hypertrophy without valvular lesions, the abnormal power of the heart's action can be diminished by the regulation of diet and sedative remedies. In all cases, while the body should be well nourished, it is desirable to prevent or remove, by dietetic and other measures, that morbid condition of the blood known as plethora. Within the past few years a class of remedies - the bromides of potassium, ammonium, sodium, and calcium - have been introduced, which appear to diminish, by an effect npon the vessels, the amount of blood within the head. These remedies, at all events, have been found by experience to be useful in cases of cerebral congestion. In severe cases, characterized by active delirium or apoplectic coma, bloodletting will not only produce speedy relief, but, timely resorted to, it may rescue from impending death. If the symptoms and danger do not call for this potent measure, an active cathartic, especially croton oil, is promptly effective. Ligatures applied to the extremities may sometimes be substituted for bleeding.

Cold applied to the head, in the form of either the douche or ice cap, is highly useful, and with these may be conjoined warm and stimulating applications to the extremities. Passive congestion, that is, an overplus of venous blood within the skull, is an effect of various causes which interfere with the return of blood from this part of the body. The pressure of the thyroid bodies when greatly enlarged (goitre), enlarged lymphatic glands, and tumors in the neck pressing on the jugular veins have this effect. Aneu-rismal or other tumors within the chest produce the same effect by pressure on the descending vena cava. A not infrequent cause belonging in this category is an obstruction to the passage of the blood into the right side of the heart, the obstruction being due to dilatation of the right auricle and ventricle, resulting from an obstacle to the circulation through the pulmonary organs, incident either to valvular lesions at the mitral orifice within the heart or to affections of the lungs themselves. Of the latter, pulmonary emphysema is the affection which especially leads to this result. Passive congestion from these causes, even when considerable, is often tolerated without great inconvenience.

The face is more or less congested, and if the congestion be great, there may be lividity or blueness especially marked in the space over the lips intervening between the skin and mncous membrane, which is called the prolabia. As regards the symptoms referable to the brain, passive congestion occasions a dull pain, a sense of fulness, sluggishness of the perceptions and the intellectual faculties, and defective or disturbed sleep. Occurring as an effect of the causes which have been named, the condition admits of relief only so far as these causes can be diminished; and in many cases this is impracticable. There is another cause of passive congestion within the skull, incident to the fact that the brain is removed from atmospheric pressure owing to the solidity and occlusion of the bones of the cranium, and also to the fact that the brain is not compressible to much extent by the forces which govern the intracranial circulation. The cranium forming a closed box capable of resisting the pressure of the atmosphere, and the substance of the brain not yielding much to the pressure of blood within the vessels, it follows that whenever the supply of arterial blood is lessened, a suction force is exerted upon the blood in the veins, and more or less passive congestion of the brain is a consequence.

Passive congestion, thus produced, is supposed to be a morbid element in affections which involve a diminished supply of blood to the head. The latter is an effect of impoverishment of the blood and of deficient power of the heart's action. This element is supposed to account for certain head symptoms occurring especially in children affected with cholera infantum. The blood in this affection is impoverished by profuse discharges from the stomach and bowels, and the heart's action becomes enfeebled thereby. These head symptoms, namely, morbid somnolency, semi-coma, and sometimes convulsions, were formerly considered to denote either inflammation of the meninges of the brain or serous effusion, affections which were embraced under the name hydrocephalus; hence, as simulating these conditions, the passive congestion produced in the manner just stated has been called the hydrencephaloid affection. The proper treatment of this affection embraces measures to restore the normal condition of the blood and the strength of the heart by alimentation, tonic remedies, and the judicious use of alcoholic stimulants. The treatment heretofore employed, based on the supposition of inflammation and effusion, was not only without good effect, but hurtful.

It must be admitted that in cases of passive congestion from a deficiency of the supply of arterial blood, it is not certain how far the morbid phenomena are attributable to the congestion, and how far directly to the lack of the arterial blood. II. Cerebral Anaemia. The term anaemia is used in medical writing and conversation to denote a morbid condition of the blood, namely, a paucity of the red globules. This is the condition which is understood when the blood is said to be impoverished. The term also denotes a morbid deficiency of blood in any of the organs of the body. The name cerebral anaemia implies the latter sense of the term. The affection therefore consists in a morbid deficiency of blood within the skull. The anaemia from certain causes is general, that is, it affects the entire contents of the skull; or it may be limited to a portion of the brain, the latter being incident to causes affecting branches of the intracranial arteries. An effect of general cerebral anaemia, existing in a marked degree and suddenly induced, is the occurrence of syncope, fainting, or swooning. In this condition there is loss of consciousness, the face becomes deadly pale, and there are convulsive movements with gasping for breath, the person appearing to be upon the brink of dissolution.

The condition, indeed, is but a slight remove from death. Prolonged syncope may occasion sudden death; but in general, after a brief period, the circulation within the skull is restored, and consciousness returns. The cerebral anaemia in attacks of syncope is usually caused by a suddenly induced weakness of the heart's action, and this may be occasioned by various causes. A powerful mental emotion may so affect the action of the heart as to cause an attack of syncope. The rapid loss of blood is a cause. Assuming an erect posture after recumbency from disease is another cause. Impoverishment of the blood, or the morbid condition of this fluid known as anaemia, favors the operation of the different causes which, by enfeebling the action of the heart, gives rise to syncope. The measures to be employed in syncope are those which tend to increase the power of the heart's action, and determine a flow of blood to the head. The body should be immediately placed in a recumbent position, with the head low. The impression produced by dashing cold water in the face excites the action of the heart, and often arouses instantly the consciousness.

When consciousness returns, an ethereal or alcoholic stimulant may be given, and repose for a time should be enjoined. - General cerebral anaemia, greater or less in degree, and more or less persisting, is referable to various causes, such as compression of the arteries going to the head, valvular lesions of the heart involving obstruction and regurgitation, and feebleness of the heart's action incident to different pathological conditions. The symptomatic effects are drowsiness, inability to sustain mental efforts, pain in the head, ringing in the ears, and sometimes mental hallucinations and illusions. With reference to their effects, it should be added that, as stated under the head of passive congestion of the brain, a morbid fulness of the veins within the skull, compensatory for a deficiency of the supply of arterial blood, is inferred from the fact of the contents of the cranium being removed from atmospheric pressure, together with the incompressibility of the cerebral substance; so that it is not certain how far these effects are due, on the one hand, to anaemia, or, on the other hand, to venous congestion. - Partial cerebral anaemia, that is, anaemia limited to a portion of the brain, is a morbid condition over which much light has been shed within the past few years by the researches of Kirkes, Virchow, and others.

The arteries of the brain, beyond what is known as the circle of Willis, do not inosculate freely with each other. Hence, if an arterial branch be obstructed, the distribution of blood within the area of the cerebral substance supplied by the obstructed vessel is arrested for a time; and this defective supply of blood may lead to impaired nutrition, ending sometimes in the loss of vitality or a condition analogous to gangrene. Now, the arterial branches distributing blood to the different portions of the brain are liable to be obstructed, first, by the coagulation of blood within them, and second, by a mass of fibrine or a detached vegetation either from the left cavities of the heart or from an artery situated between the heart and the brain. The obstructing substance in the first of these two modes is called a thrombus, and the morbid condition is known as thrombosis; in the second mode the obstructing substance is called an embolus, and the condition embolism; hence, a thrombus is a stationary, and an embolus a migratory plug. Thrombosis is apt to take place in the vessels within the skull, the coagulation of the fibrine of the blood being due to changes in the arteries which roughen the inner surface of these vessels.

The fibrine is liable to coagulate on a roughened surface over which the blood flows. This is shown by the experiment of inserting a needle or a thread within a blood vessel; masses of fibrine collect upon the foreign substance. Embolism occurs oftener than thrombosis. Fibrine, a product of thrombosis in the left cavities of the heart, in one of the arteries leading from the heart to the head, or .in an aneurismal sac, is liable to become separated by the force of the circulating blood, and it is then carried along with the current into the cerebral arteries, until at length it reaches a vessel too small to admit of its passage further onward; it is thus arrested in its course, and, becoming fixed, it obstructs the circulation in the branches given off beyond the point where it remains. Hence, a partial anaemia, which is more or less circumscribed according to the size of the obstructed artery. The same thing occurs when the embolus or plug is a morbid growth or a vegetation, instead of a mass of fibrine. Both thrombosis and embolism occur in various parts of the body, as well as within the skull.

In the latter situation, the artery most likely to become obstructed, especially by an embolus, is the middle cerebral; and embolism is far more likely to take place in the left than in the right middle cerebral artery, because the embolus generally comes from the heart, and the most direct route from the latter organ to the brain through the arteries is on the left side. Thrombosis and embolism give rise to that form of paralysis distinguished as hemiplegia, namely, paralysis affecting the limbs and often the face on one side. The paralysis from embolism occurs suddenly, being a stroke of palsy, because the obstruction occurs suddenly. Often with the sudden palsy there is a temporary loss of consciousness, constituting an apoplectic seizure. This is one of several different morbid conditions giving rise to sudden coma or apoplexy. In a certain proportion of cases, the paralysis disappears completely after a time, the circulation being more or less slowly restored beyond the point of the obstruction. Recovery takes place if the circulation be restored before important changes in nutrition have resulted from the deficient supply of blood.

Softening and even complete loss of vitality of cerebral substance within the space deprived of arterial blood take place in some cases, and more or less hemi-plegic paralysis then remains. Hemiplegia, either transient or persisting, is in like manner an effect of thrombosis. It is generally developed gradually, and is not so likely to give rise to sudden coma or apoplexy, because, the coagulation not taking place all at once, the obstruction occurs more or less gradually. III. Cerebral HAEmorrhage. Haemorrhage within the cranium may take place, first, either into the substance of the brain or the spaces known as the ventricles, and second, between the membranes investing the brain. The name cerebral haemorrhage is applied especially to an extravasa-, tion in the two former of these situations. Situated between the membranes, it is distinguished as meningeal haemorrhage. Haemorrhage very rarely takes place primarily within the ventricles of the brain; when blood is found here, the seat of the extravasation is generally in the cerebral substance, and the blood has thence made its way into the ventricles. Haemorrhage is the most frequent of the several morbid conditions giving rise to the sudden loss of consciousness which characterizes an apoplectic attack.

In the great majority of the cases of apoplexy caused by this condition, the haemorrhage takes place in the substance of the brain. The extravasation is seated in either the corpus striatum or the thalamus opticus much oftener than in any other of the anatomical divisions of the brain; it may, however, occur in any portion of the cerebral substance. The quantity of blood which escapes varies greatly in different cases. If very large, death may occur within a few hours. Sudden or almost instantaneous death, however, is very rarely if ever caused by cerebral haemorrhage. If the extravasation be small, the patient emerges after some hours from the coma or apoplectic state; the clot may subsequently be absorbed, and recovery may take place, with more or less permanent injury of the brain. An apoplectic attack dependent on haemorrhage into the substance of the brain is almost always accompanied by paralysis of the muscles of the limbs, and generally also of certain of the muscles of the face on one side of the body (hemiplegia). This is always a concomitant of an extravasation into the corpus striatum, or the motor tract of the fibres of the brain. The paralysis of the limbs, and generally also of the face, is on the side opposite to the cerebral hemisphere in which the haemorrhage is seated.

In some cases in which -the extravasation is small, or in which it takes place slowly, hemiplegia, without apoplexy, is the effect. Hemiplegia, in the cases of apoplexy dependent on haemorrhage into the substance of the brain, persists after the apoplectic state disappears; and in general this form of paralysis in a greater or less degree continues permanently, even when the ex-travasated blood has been absorbed. After an apoplectic attack from cerebral haemorrhage, the mental faculties generally become more or less impaired. The degree of impairment will depend on the amount of injury which is the immediate effect of the haemorrhage, and on the disorganization due to the inflammation excited by the presence of the clot. It is also to a certain degree dependent on the diminished exercise of the mental faculties which is usual after an attack of apoplexy. Cerebral haemorrhage is generally a consequence of disease of the arteries of the brain. They are liable to become instantaneously fatty, and to be rendered brittle by the deposit of calcareous matter. Hence, either with or without some unusual tension, such as is caused by violent muscular efforts or intense mental excitement, they give way, and extravasation occurs.

Another condition favoring rupture is the formation of minute dilatations, which are called miliary aneurisms. These changes in the arteries rarely take place prior to middle age; hence, apoplexy and hemiplegia dependent on cerebral haemorrhage seldom occur in youth. - During an attack of apoplexy dependent on extravasation of blood, little is to be done in the way of treatment beyond keeping the body of the patient quiet, with the head raised, removing all articles of clothing which make pressure on the neck or chest, and applying cold to the head. Bleeding under these circumstances, which was formerly resorted to, is now rarely employed. An active cathartic is generally given. If the patient emerge from the comatose state, the objects of treatment are the promotion of absorption of the clot, the prevention of a repetition of the haemorrhage, and the recovery as far as practicable from the paralysis. As the changes in the vessels which occasioned the haemorrhage continue, its recurrence is always to be apprehended. Yet not unfrequently life continues for many years and a second haemorrhage does not occur. It is important to add that cerebral haemorrhage is seldom preceded by premonitory symptoms.

Hence, in general, vertigo, ringing in the ears, and other symptoms which naturally lead persons to anticipate an attack of apoplexy, are not to be thus interpreted. Much relief from needless apprehensions may often be afforded by recollecting the statement just made. - Haemorrhage situated between the membranes of the brain, or meningeal haemorrhage, is extremely infrequent in comparison with extravasation in the cerebral substance. This statement is especially true if cases in which meningeal haemorrhage is attributable to injuries received on the skull be excluded. The latter are distinguished as traumatic cases. Excluding these, the seat of' the haemorrhage is generally beneath the arachnoid membrane. The blood escaping in this situation may be more or less diffused over the surface of the brain, remaining beneath the arachnoid membrane; or this delicate membrane may be ruptured, and then the blood is diffused over the brain within the arachnoid cavity, between the arachnoid and the dura mater. A small quantity of blood in this situation may not give rise to serious results, and it may even be unattended with any violent symptoms referable to the head.

A considerable haemorrhage here, however, occasions insensibility or coma, which is developed suddenly or gradually, according to the rapidity as well as the amount of the haemorrhage. The patient may emerge from this coma, and if the haemorrhage recur, as is sometimes the case, the coma is again renewed. Usually, owing to the diffusion of the blood over the surface of the brain, there is not hemiplegia, as in cerebral haemorrhage. Death may be expected to take place if the amount of the haemorrhage be sufficient to occasion a prolonged or repeatedly recurring coma. - A form of meningeal haemorrhage occurring independently of traumatic causes is known as haematoma of the dura mater. In this form, the blood is under the dura mater, and is contained within oval fibrinous sacs several inches in diameter and three or four inches thick. These are generally found on the upper surface of both hemispheres of the brain. The fibrinous sacs are supposed to denote inflammation. This affection occurs in children and in aged persons; but it is rare, and not determinable with certainty during life. Sooner or later it ends fatally, after having induced diminished power of motion of the limbs on both sides and stupor, which at length eventuates in coma.

IV. Inflammatory Affections. In the comprehensive sense of the phrase " diseases of the brain," inflammatory affections may be seated in either the membranes or the cerebral substance. Their primary seat is much oftener in the former than in the latter. Of the membranes investing the brain, the dura mater is very rarely inflamed. An inflammation seated in this, the outer of the cerebral membranes, or the meninges, is almost always limited to a circumscribed space, and is produced either by an injury of the head (traumatic), or by an extension of disease from a contiguous part of the skull. An idiopathic or spontaneous primary inflammation of this membrane perhaps never occurs, if the affection called haematoma of the dura mater be excluded. The term cerebral meningitis denotes inflammation of the membranes or meninges of the brain; but the term is considered as embracing only inflammatory affections seated in the pia mater and arachnoid membrane. Inflammation affects these two membranes conjointly; that is, whether the point of departure be in the one or the other, both are involved. Cerebral meningitis is acute, subacute, or chronic. In addition, a variety of the disease is called tuberculous meningitis.

The term simple meningitis is used to distinguish an ordinary inflammation from the variety called tuberculous. Exclusive of traumatic cases, that is, those in which the disease is produced by injury from falls or blows, causes of simple acute meningitis are insolation, or exposure to great heat, and excessive indulgence in alcoholic stimulants. These causes are chiefly operative when adults are affected with the disease. Acute inflammation from other causes than these, and from injuries of the head, occurs oftener in children than after adult age. In children it is sometimes developed in the course of scarlet fever, erysipelas, and measles. But simple acute meningitis, irrespective of traumatic cases, is extremely rare. The symptoms of acute meningitis are at the beginning essentially the same as in active cerebral congestion; and this, indeed, is the pathological condition. The prominent local symptoms are intense, diffused pain in the head, flushing of the face, notable intolerance of light and sounds, an increase of the sensibility of the surface of the body (hyperesthesia), throbbing of the arteries of the neck and head, and delirium, which is often active or violent. Hallucinations, as well as delusions, enter into the delirium.

With these local symptoms, there is symptomatic fever, as shown by frequency of the pulse, increased heat of the skin, and, more especially, augmented temperature of the body as denoted by the thermometer placed in the armpit. Convulsions sometimes occur. Other symptoms denoting constitutional disturbance are loss of appetite, often vomiting, constipation, disturbed rhythm of respiration, and more or less debility, except when the patient is under the excitement of delirious volitions. These symptoms belong to the first stage, or the stage of excitement, the duration of which varies from a few hours to several days. The symptoms which distinguish the second stage are due mainly to compression of the brain by the inflammatory products, lymph, serum, and pus, which are situated for the most part beneath the arachnoid membrane. These symptoms are somnolence ending in coma, paralysis of certain of the facial muscles, and sometimes of the muscles of the limbs, on one side, dilatation of the pupils, slowness and irregularity of the pulse, etc. These symptoms generally denote a fatal ending. This stage is distinguished as the stage of compression and of collapse. Simple acute meningitis is always a disease involving great danger to life. A very large proportion of cases end fatally.

Life may be destroyed speedily, sometimes within a few hours. In most fatal cases the duration of the disease does not extend beyond a week. The measures of treatment which are appropriate to the first stage are: bloodletting by venesection and leeching, if there be no circumstances to contra-indicate the abstraction of blood; cold applied to the head by means either of cloths wetted at short intervals in ice water, the cold douche, or the ice cap; and active purgation. As remedies which appear to diminish the blood within the skull, the bromides are to be recommended, clinical'experience having shown their utility. In the second stage, the great object of treatment is to promote the absorption of the morbid products. Mercury and the iodide of potassium are prescribed for this object. Blisters may be employed for the same end. Alimentation, to an extent corresponding with the ability to take and digest nutritious food, enters into the treatment in the second stage. - Acute cerebral meningitis may be associated with an acute inflammation of the corresponding membranes of the spinal cord. The affec-tion is then called cerebro-spinal meningitis. This characterizes a remarkable and extremely fatal epidemical disease, generally known by the name epidemic cerebro-spinal meningitis.

A subacute simple cerebral meningitis, in which the inflammation does not become chronic, is infrequent; but cases occur, chiefly in children. The symptoms in the stage of excitement are the same in character as in the acute disease, but notably less marked or intense. The symptoms due to compression may be developed after a slight or moderate headache, intolerance of light and sounds, febrile movement, etc.; and a fatal coma may be caused by an abundant serous effusion. The treatment in these cases relates chiefly to the absorption of serous effusion. - Subacute inflammation of the meninges of the brain is generally presented as a chronic affection, and is called chronic cerebral meningitis. The local symptoms are pain in the head, muscular weakness, undue disposition to sleep, change in the mental disposition or character, more or less impairment of the intellectual faculties, paralysis affecting sometimes certain of the facial nerves, and in some cases the two limbs on one side; and at length, in the great majority of cases, a fatal termination occurs, preceded by great exhaustion and frequently by coma. This affection may follow acute meningitis, but in general the inflammation is subacute from the outset.

It is often latent; that is, it is not declared by well marked symptoms pointing to inflammation within the skull; and it is, therefore, liable to be confounded with other affections. Mental irritability and dulness of the faculties of the mind may for some time be the only symptomatic characters referable to the head. Moreover, it is by no means always easy to discriminate by the symptoms this affection from softening and other cerebral lesions. The duration of the disease is often long, not infrequently lasting many months, and even years. Sooner or later, it ends generally in death. The causes are usually obscure. Happily rare. There is not much prospect of benefit from drugs; but certain remedies, namely, mercury and iodine, may be tried. The great object of treatment is to maintain nutrition and thus enable the system to tolerate the disease as long as possible. - In tuberculous meningitis, the inflammation of the meninges is referable to the presence of tubercles or miliary granulations. . These morbid products are seated at the base of the brain, and hence the inflammation is limited to or most marked at the base; whereas, in simple meningitis, the upper portion or convexity of the brain is chiefly or especially the seat of the inflammation.

The ventricles of the brain in this affection are apt to contain liquid in more or less abundance, and hence formerly the affection was called acute hydrocephalus. The affection is vastly more frequent in infancy and childhood than in after periods of life, but it occurs at all ages. It is almost invariably associated with tubercles in other organs, and especially in the lungs. In general, the development of this affection takes place gradually. For some weeks or months before the disease becomes declared, children generally show symptoms of ill health, namely, loss of appetite, indisposition to exercise, and more or less emaciation. Especially a mental change is noticeable, consisting in irritability of temper and dulness of the faculties of the mind. These symptoms probably relate to the tuberculous disease, and precede the acute inflammation. The latter is characterized by headache, generally intense and persisting, accompanied often by persistent vomiting; there is usually intolerance of light and sound; the face is apt to be flushed in paroxysms; there is fever, as shown by the pulse and temperature of the body.

These symptoms continue for a period ranging from a few days to a fortnight; and then a change occurs which is attributable mainly to the presence of the inflammatory products, lymph, pus, and serous effusion. The pulse is now diminished in frequency, and it may fall considerably below the healthy standard; it is apt also to be irregular and faltering. The respiration is altered in rhythm, becoming irregular and suspirious. The pupils are dilated. The perceptions are blunted; the patient lies most of the time in a state of somnolency. Lancinating pains in the head are, however, felt from time to time, giving rise in infants to a sudden sharp cry which is quite distinctive. The temperature of the body may now fall below the minimum of health. The vomiting becomes less, or it may cease. The bowels are constipated, and the abdomen depressed. Convulsions, which sometimes occur before, are not infrequent after this change in the symptoms has taken place. Strabismus or squinting is common. Paralysis of the muscles of the face or of the limbs on one side is frequent. At length vision is lost; the somnolency eventuates in coma, and, under these circumstances, the affection ends fatally.

The tendency to death is such, that when this affection is considered to exist, recovery is a ground for the rational presumption that the affection was not really present, but simulated. In children, it is liable to be confounded with typhoid fever, and with a condition already referred to, namely, cerebral anaemia incident to disorder of the digestive system. Moreover, it is not always easy to discriminate it from a simple acute meningitis. The iodide of potassium has been of late years chiefly relied upon in the treatment of tuberculous meningitis. Its efficacy, however, in any case is questionable; and there are no remedies at present known which can be given with any expectation of effecting a cure. The only hope, in cases which seem to present the evidence of existence of this affection, is that the diagnosis may be incorrect. Blisters, active purgatives, and other debilitating and perturbatory measures of treatment are not only not indicated, but they increase suffering and hasten the fatal termination. - Inflammation either limited to or having its point of departure in the substance of the brain is known as cerebritis. As already stated, the substance of the brain is more or less involved in meningitis.

Independently of the latter, cerebritis is rare; and if the cases be excluded in which inflammation of the substance of the brain is secondary to tumors or to the presence of a clot, or is incident to injuries, it is extremely infrequent. In fact, a primary or idiopathic cerebritis is one of the rarest of affections. Its infrequency has been rendered more evident within late years by the knowledge which has been acquired of necrobiosis, or softening from embolism and thrombosis, to which reference has been made under the head of anaemia of the brain. Oases of the latter kind of softening were formerly considered as cases of cerebritis. The presence of blood giving rise to "red softening" has been considered as, evidence of inflammation; but this is now held to be an error. Softening from defective nutrition may be red as well as white. The positive evidence of cerebritis is the presence in the cerebral substance of the inflammatory products, fibrine or pus. Cerebritis, as a primary or idiopathic affection, is always circumscribed, or confined to a limited space. It occurs chiefly in the gray matter of the brain, that is, in the cortical portion of the corpus striatum. If pus be present, it is called abscess of the brain.

The symptoms and the duration in different Cases entitle it to be considered either an acute or a chronic affection. If acute, pain in the head is more or less prominent as a symptom, and there are present the symptoms denoting hyperemia or cerebral congestion. Spasms of certain muscles, either tonic or clonic, may occur, and sometimes there are general convulsions. Subsequently, when the inflamed portion becomes disorganized, that is, when softening or the formation of an abscess ensues, paralysis generally occurs. The paralysis is developed gradually, and in different cases different muscles are affected. In most cases the muscles of the face are paralyzed in a greater or less degree, and hemiplegia is common. The mental faculties become impaired, as denoted first by a morbid emotional susceptibility, and afterward by loss of memory and inability to carry on processes of ratiocination. At length mental imbecility or dementia is likely to occur. Chronic cerebritis, or abscess of the brain, presents the same symptoms which belong to the acute form after softening or suppuration has taken place.

The points of distinction, as regards the symptomatology, between the acute and chronic affection, relate to the presence of symptoms denoting more distinctly an inflammatory condition in the former, and a longer duration of the disease in the latter. Chronic cerebritis or abscess is not easily discriminated during life from other affections which are to be noticed presently under the head of structural lesions. Cerebritis, both acute and chronic, is generally secondary to injuries of the skull, or to disease of the bones of the head. It is apt to follow caries of the petrous portion of the temporal bone, the latter being connected with inflammation of the internal ear. It may fairly be doubted if recovery ever takes place. Chronic cerebritis, however, leading to softening or abscess, is not incompatible with a long duration of life, death at length occurring, perhaps, in consequence of some intercurrent disease. The indications for treatment relate to palliative measures, and those which enable the system to tolerate the affection as long as possible. V. Structural Lesions. Lesions involving palpable changes in structure, affecting the brain more or less extensively, and with different degrees of damage, are of various kinds.

Important lesions have already been referred to, namely, softening from defective nutrition, and either inflammatory softening or suppuration. Another lesion, probably of inflammatory origin, is induration or sclerosis. Other lesions are the morbid growths or deposits which constitute the different tumors of the brain. These various structural changes have certain symptoms in common, and in medical practice it is by no means easy always to differentiate them. Induration of the brain, on sclerosis, may be confined to one situation which is more or less extensive, or it affects small circumscribed portions which are more or less numerous. The former is distinguished as diffused, and the latter as multiple cerebral sclerosis. The diffused form most frequently occurs in children, although it may occur at any period of life. It is a pathological condition which in certain cases affords an explanation of idiocy. It leads to paralysis, and consequently to an arrest of development of certain of the voluntary muscles. It may lead to contractions and deformities in consequence of the extensor muscles being more paralyzed than the flexors, or vice versa; the muscles which are the least paralyzed contracting for want of the normal antagonism afforded by those in which the paralysis is greatest.

In multiple cerebral sclerosis, hardened nodules, varying in size from a cherry stone to a small walnut, and more or less numerous, are scattered throughout the brain, generally being found in the white substance. They are produced by a morbid growth of the connective tissue, that is, the tissue which unites the nervous fibres and cells together with the blood vessels. This tissue is now known by the name neuroglia. Its morbid growth is supposed to be a consequence of chronic inflammation. The hypertrophied neuroglia induces by pressure atrophy of the nervous structure, and consequently impairment of function in the sclerosed portions. The causes are obscure; but circumstances connected with age have , a marked influence on the causation. It very rarely occurs in persons under 50 years of age. Muscular tremor, beginning slightly in a few muscles and gradually increasing and extending, is one of the most characteristic of the symptoms. After a time the limbs and sometimes the head are involved in the tremor, which at first can be arrested by volitional efforts, and exists only in the waking hours, but at length continues in spite of the will and during sleep. Paralysis greater or less in degree follows the tremor.

The name paralysis agitans, or shaking palsy, has been applied to these cases. Prior to and with these symptoms lancinating pains in the head are common. Distortion of the limbs may occur from the paralysis affecting certain muscles (generally the flexors) more than others. Certain cases present remarkable peculiarities in the mode of progression. Thus some patients are able to run forward rapidly when they cannot walk, and are obliged to support themselves by clinging to some solid body in order to prevent themselves from falling when they stop. In other cases patients are able to walk backward, but not forward. The course of this affection is usually slowly progressive; yet in some cases it remains stationary. Existing in a marked degree, it may not prevent long life. A cure is not to be expected; but improvement is sometimes effected by the chloride of barium, the phosphide of zinc, strychnia, and electricity. The tolerance and duration of life are promoted by measures which tend to improve the general health, and maintain it at the highest possible point. Multiple sclerosis of the brain is not infrequently associated with a similar affection of the spinal cord. - Tumors within the cranium have the different anatomical characters which belong to tumors in other situations.

The most frequent are those distinguished as cancerous, tuberculous, and syphilitic. Others which are comparatively rare are aneurismal, fibro-plastic, and parasitic, the latter consisting of the cysti-cercus or hydatids. There are still others which are occasionally found. The different tumors vary in number, size, and situation. There may be but one tumor, or the number may be great; in the latter case, they are usually small. They may be very small, not exceeding the size of a pin's head, or they may be as large as an orange, or even larger. They may be seated in different portions of the cerebral substance, or they may have their point of departure from the membranes, and sometimes from the bony structure. They produce morbid effects, or symptoms, by pressure on the cerebral structure together with the nerves within the skull, and by giving rise frequently to circumscribed inflammation, which may lead to either induration or softening. The more grave of these morbid effects are paralysis affecting different parts, and more or less impairment of the intellectual faculties. Convulsions belong among their effects. They are generally accompanied with pain localized within a circumscribed space, and vertigo is not uncommon.

The system suffers in proportion to the amount of the injury which the brain receives, and frequently also from the general condition with which the local affection is associated. The latter applies especially to cancerous and tubercular tumors. Sooner or later, as a rule, they destroy life. The local symptoms which denote especially tumor within the skull are a localized persistent pain, and the occurrence of paralysis affecting different parts successively, after intervals of varying duration. Frequently, but not always, these points suffice for a positive diagnosis of tumor of some kind. The associated circumstances, such as tuberculous or cancerous disease elsewhere, or the fact of syphilis having existed, enable the physician to decide with considerable confidence on the nature of the tumor. Moreover, its situation may frequently be inferred from the parts which are paralyzed, together with the amount and kind of mental disturbance. With our present knowledge, curative treatment is limited exclusively to syphilitic tumors. The effect of anti-syphilitic medication, where the symptoms denote the existence of tumor of this kind, is sometimes remarkable. It is, therefore, highly important that the physician should know the grounds for supposing the tumor to be syphilitic in character.

Mercury and the iodide of potassium are the remedies indicated if the tumor be syphilitic. - A curious morbid condition, incident to different structural lesions, and sometimes occurring as a functional affection, may be noticed in this connection. Reference is had to the condition now generally known as aphasia. This term signifies loss of speech, not from any affection of the organs concerned in phonation, but from either an inability to remember words, or a want of power to coordinate the movements involved in speech. As thus defined, aphasia is to be distinguished from aphonia, the latter term denoting loss of voice from an affection of the vocal apparatus, or from a paralysis affecting the muscles concerned in phonation. In aphasia the vocal organs are unaffected, and the patient has voluntary control over the muscles of the larynx and mouth. Nor is aphasia to be confounded with loss of speech in consequence of dementia or mental imbecility. Patients affected with aphasia understand what is said to them, and they are able to read; but the ability to express their ideas in language is lost or more or less impaired. A marked difference exists among different cases of aphasia.

In some, while the patient is unable to speak, there is the ability to communicate their ideas by writing; in other cases, the patient can neither speak nor write. Hence, according to this difference, aphasia is of two kinds, namely, amnesic and ataxic. In amnesic aphasia both speaking and writing are lost or impaired; in ataxic aphasia speech is lost, but the ability to write remains.

In the first kind, the difficulty consists in the loss of the memory of words; in the second kind, the difficulty seems to lie in the inability to coordinate the movements necessary to speech, the memory of words being preserved. Aphasia of either kind may be complete, when speech is entirely lost, or there is more or less impairment of the power of speaking. Frequently the vocabulary of the patient is limited to a few words, perhaps a single word, uttered whenever an attempt is made to speak. Thus, patients may be able to say only yes or no, and this is said in answer to any question. It is not easy to determine, in cases of aphasia, to what extent, if at all, the mental powers are affected; but it is certain that complete aphasia may exist while the faculties of the mind, aside from speech, are not materially affected. As already stated, aphasia may be incidental to different structural lesions, namely, haemorrhage into the substance of the brain, softening from embolism or thrombosis, cerebritis, induration, and tumors. Generally it is associated with hemiplegia, and the paralysis is usually on the right side, the local affection of the brain being situated in the left hemisphere.

And now a remarkable fact is to be stated: the lesion giving rise to aphasia in the great majority of cases is seated in a particular portion of the left cerebral hemisphere, namely, the posterior part of the third convolution of the anterior lobe of the cerebrum. This fact has led to the supposition that the portion of the left hemisphere first named is to be regarded as the seat of the faculty of language; but, as opposed to this, although the rule is as stated, there are some exceptions to it. Evidently, if the faculty of speech depended on the integrity of a particular part of the brain, that part should be affected in all cases of aphasia. Aphasia is generally a symptom of a lesion of some kind; and it is then almost always persistent. There may, however, be some improvement as regards speech, although recovery do not take place. In some cases it is apparently dependent on a functional condition, and it is then recovered from. Aside from the measures of treatment which may be indicated by the nature of the lesion with which it is associated, or the circumstances connected with it when it is functional, efforts to speak on the part of the patient should be enjoined.

Something may be accomplished by systematic endeavors to recover the memory of words or the power of coordinating the movements involved in speaking. VI. Functional Disorders. The term functional disorder, as now used, denotes a morbid disturbance of functions taking place independently of either inflammation or any palpable alteration of structure. It is convenient to arrange certain affections under this head, notwithstanding it is doubtless true that every so-called functional disorder involves some structural change. Admitting this, a disorder is to be distinguished as functional if it be non-inflammatory, and the circumstances are such as to exclude all the different varieties of structural change which morbid anatomy, in the present state of our knowledge, recognizes. With this definition, what are the functional disorders referable to the brain? The different kinds of mental derangement - mania, monomania, melancholia, dementia - may be considered as varieties of functional disorder of the brain. (See Insanity.) In this statement it is implied that, in a certain sense, the normal intellectual and emotional faculties are to be regarded in the light of cerebral functions.

We may assume such to be the fact, without any skepticism as to -the existence of the soul, in which consists personality, and which will sur -vive the body, albeit it is in the order of Providence that in the present life the exercise of the mental faculties, and even the consciousness of being, are dependent on the physical organism. The phenomena embraced under the name delirium, and the more or less complete loss of consciousness and volition called coma, are evidences of functional disorder of the brain occurring in connection with various diseases, without involving either cerebral lesions or inflammation. These forms of functional disorder occur in fevers, and also in various local affections. Under these circumstances the brain is functionally disordered in consequence of morbid conditions of the blood. Thus the delirium of typhus and typhoid fever is referable to those blood changes, imperfectly understood as yet, in which consists the essential pathology of these diseases; and the coma occasioned by certain diseases of the kidneys is an effect of an accumulation of urea in the blood, or uraemia. Various remedies, by a toxical effect on the brain, may give rise to functional delirium or coma. This is true of opium, belladonna, and other narcotics, chloroform, etc.

The phenomena of drunkenness denote functional disorder due to the presence of alcohol in the blood which circulates within the skull. There are certain nervous affections distinguished as functional, and called the neuroses, in which the functions of the brain are perverted or impaired; examples are epilepsy, hysteria, hydrophobia, and ecstasy. Finally, irrespective of all the foregoing affections, the faculties of the mind are often affected, but not sufficiently to constitute either coma, delirium, or insanity, and certain cerebral symptoms occur as results of functional disorder of the brain. Mental depression, irritability of temper, painful sensations referable to the head, vertigo, and wakefulness are manifestations of functional disorder due to over-exercise or excitation of the mental powers, intellectual or emotional, prolonged anxiety, impoverishment of the blood (anaemia), and probably by various morbid conditions of the latter incident to disordered assimilation, the retention of matters which should be eliminated by the different excretory organs, or the introduction of morbific principles by means of the air.

The relations of" functional disorder of the brain to the happiness of individuals and the welfare of mankind is a subject of much importance, to which only this simple reference is here appropriate.