100 INSANITY tion of brain structure. If, however, we give due weight to the results of physiological research, the matter is not quite so obscure. Arguing from the analogies of other organs and from direct observation, there is reason to believe that when the brain functions are being actively exerted there is a dilatation of the vessels and an increased blood supply (hyperaemia) to its superior and lateral surfaces. This functional hyperaemia is caused by the direct action of the cerebral cells, which, along with the sympathetic system of nerves, exercise control over the muscular coats of the arteries, the immediate regulators of blood supply to any given part. Control over muscular tissue implies, of course, control in two directions, dilatation and contraction. Functional hyperaemia is in every respect a healthy condition, one necessary for the provision of, temporary nutriment during temporary action, ceasing with the withdrawal of stimulus, when the calibre of the vessels is reduced to its original dimensions through the contracting influence of the cells. But if the excitement is unduly prolonged a new result appears ; the cells themselves become exhausted, and therefore, even if the stimulus is withdrawn, they are unable to assert their ordinary control over the arterial muscular coats in the direction of con traction, so that the increased blood supply continues although the stimulus which caused it has been removed. Instead of functional hyperaemia we have a hypersemia caused, not by functional excitement, but by exhaustion of the controlling organs. In a minor degree the results of this condition are matters of everyday observation ; over taxation of the brain functions, by study for instance, is very generally followed by sensations of fulness and aching of the head, loss of sleep, and general exhaustion, a condition which is recovered from when the primary irritation is withdrawn, i.e., when the arteries reacquire healthy tone. But if relief from the causes of irritation is not obtained, a sequence of events ensues tending to deterioration of tissue. In the first place, sleep, the condi tion necessary for rest and recuperation of the cells, becomes unattainable. Physiological research has shown that during sleep the supply of blood to the brain is diminished (anaemia), that anaemia is necessary for, and hyperaemia is inimical to, its production. Further deterioration of cell activity follows on non-recuperation, and concomitant diminished control over the vessels tends to the establish ment of morbid hyperaemia and more or less blood stagna tion (stasis). It would be far beyond the compass of this article to follow out in detail the various pathological processes which ensue on paralysis of vaso-motor action ; two only need be alluded to (1) the various changes which take place in the behaviour of the constituents of the blood, producing congestion and greater or less obstruction to its normal distribution, and (2) the effects which congestion produces on the lymphatic system of the brain, the system by which effete matter is largely removed from it. It is now generally recognized that the lymphatics of the brain are peri vascular, i.e., that they are tubes sur rounding the arteries, patent under ordinary conditions ; when, however, the arteries are distended, it is easy to comprehend that the lymphatic system becomes occluded by the artery filling up the space provided for it, and therefore that the removal of waste products becomes difficult or impossible. It is a pathological axiom that the structural integrity of a part is dependent on the main tenance of its vascular unity, in other words, on the regular .supply and withdrawal of blood by its regular channels. This if impaired or destroyed is necessarily followed by histological changes and by disturbance of function. By this exposition of a probable sequence of pathological events it is desired to indicate that disturbance of function directly referable to over-excitation of the brain is not a mere functional derangement, not a mere morbid increase of a normal emotion, but that it is the manifestation of a pathological condition, that, in effect, so-called moral causes may be the producers of physical cerebral disease. This meets with support from the clinical observation that, with very rare exceptions, a considerable period of time elapses between the incidence of the moral cause and the first indication of mental alienation, an interval during which sleep has been absent in consequence of continued hyperaemia. Instances of melancholy or mania being suddenly produced by mental shock must be searched for in works of fiction. Sudden fright, more especially, is stated to produce immediate convulsion, epilepsy, and catalepsy, but not insanity ; except in certain comparatively rare instances, in which it appears to induce with great rapidity a cataleptic mental state, presently to be spoken of as acute primary dementia. Over-exercise of the intellectual function is not by any means such a prolific cause of brain disease as undue emotion. It is not work but worry that kills the brain. When both are combined the result is often rapid. On the removal or persistence of congestion depends the issue of a case recovery, or further and permanent solution of continuity. Unless relief is soon obtained, the changes in the cells are followed by lesions of other brain structures which are productive of important pathological conditions affecting the general system ; these in their turn render recovery more difficult or impossible, or may even cause death. (For a full account of the various lesions found in the brains of the insane, consult Bucknill and Tuke, Manual of Psychological Medicine, 4th ed., cap. vi. ; Fox s Patho logical Anatomy of the Nervous Centres, London, 1874 ; J. Batty Tuke, " On the Morbid Histology of the Brain and Spinal Cord as observed in the Insane," Brit, and For. Medico-Chirurgical Review, 1873-74.) 2. The second class comprises all accidents and injuries affecting the brain, and is most conveniently termed traumatic. Violence to the head may produce fracture of the skull with or without depression, extravasation of bloud in or on the brain, or concussion. There is no relation between the apparent extent of the injury and the results in insanity ; extensive fractures of the frontal, lateral, and superior surfaces of the skull, even when complicated with rupture of the envelopes and loss of brain matter, are not, taken over all, more productive of insanity, if so much so, as the apparently less serious condition of concussion. The reason of this is not far to seek ; by the open wound free egress is afforded for extravasated blood and the products of inflammation, whereas in concussion, which may also involve extravasation of blood in or on the brain, foreign substances have no means of escape, and so may set up morbid action of a grave nature. Occasionally insanity follows rapidly on the injury, but much more frequently weeks or even months elapse before development of mental symptoms amounting to insanity. During this period morbid action is proceeding on the inner surface of the skull, in the membranes, or in the brain itself. On the inner table of the skull bony growths may be in process of formation, subacute inflammation of the membranes may be going on, and from the same cause the brain may be undergoing progressive changes generally in the direction of sclerosis, i.e., increase of connective tissue. 3. The nervous diseases in the train of which insanity occasionally follows are Epilepsy, Hysteria, and Locomotor Ataxy. In the case of Epilepsy the brain lesions are doubt less the result of the frequently asphyxiated condition of the patient and of the blood poisoning due to the retention of carbonic acid gas (see EPILEPSY). As might be expected, lesions of the arteries in the form of hypertrophy of their coats is frequently observed. The canals in the brain
