certainly play a weighty part in producing mental, as they do in producing other nervous disorders. Lower the supply of blood to the brain below a certain level, and the power of thinking is abolished; the brain will then no more do mental work than a water-wheel will move the machinery of the mill when the water is lowered so as not to touch it. When a strong emotion produces a temporary loss of consciousness, it is to be presumed that a contraction of arteries takes place within the brain similar to that which causes the pallor of the face; and when the laboring heart pumps hard to overcome the obstruction, and the walls of the vessels are weak, they may burst, and the patient die of effusion of blood. During sleep the supply of blood to the brain is lessened naturally, and we perceive the effects of the lowering of the supply, as it takes place, in the sort of incoherence or mild delirium of ideas just before falling off to sleep. To a like condition of things we ought most probably to attribute the attacks of transitory mania or delirium that occur now and then in consequence of great physical exhaustion, as from great and sudden loss of blood, or just as convalescence from fever or other acute disease is setting in, or in the prostration of phthisis, and which a glass of wine opportunely given will sometimes cure. The distress of the melancholic patient is greatest when he wakes in the morning, which is a time when a watch ought to be kept specially over the suicidal patient; the reason lying probably in the effects of the diminished cerebral circulation during sleep.

If the state of the blood be vitiated by reason of some poison bred in the body, or introduced into it from without, the mental functions may be seriously deranged. We are able, indeed, by means of the drugs at our command, to perform all sorts of experiments on the mind: we can suspend its action for a time by chloral or chloroform, can exalt its functions by small doses of opium or moderate doses of alcohol, can pervert them, producing an artificial delirium, by the administration of large enough doses of belladonna and Indian

hemp. We can positively do more experimentally with the functions of the mind-centres than we can do with those of any other organ of the body. When these are exalted in consequence of a foreign substance introduced into the blood, it cannot be doubted that some physical effect is produced on the nerve-element, which is the condition of the increased activity, not otherwise probably than as happens when a fever makes, as it certainly will sometimes do, a demented person, whose mind seemed gone past all hope of even momentary recovery, quite sensible for the time being. Perhaps this should teach us that, just as there are vibrations of light which we cannot see, and vibrations of sound which we cannot hear, so there are molecular movements in the brain which are incapable of producing thought ordinarily, not sufficing to affect consciousness, but which may do so when the sensibility of the molecules is exalted by physical or chemical modification of them.

Alcohol yields us, in its direct effects, the abstract and brief chronicle of the course of mania. At first there is an agreeable excitement, a lively flow of ideas, a revival of old ideas and feelings which seemed to have passed from the mind, a general increase of mental activity-a condition very like that which often precedes an attack of acute mania, when the patient is witty, lively, satirical, makes jokes or rhymes, and certainly exhibits a brilliancy of fancy which he is capable of at no other time. Then there follows, in the next stage of its increasing action, as there does in mania, the automatic excitation of ideas which start up and follow one another without order, so that thought and speech are more or less incoherent, while passion is easily excited. After this stage has lasted for a time, in some longer, in others shorter, it passes into one of depression and maudlin melancholy, just as mania sometimes passes into melancholia, or convulsion into paralysis. And the last stage of all is one of stupor and dementia. If the abuse of alcohol be continued for years, it may cause different forms of mental derangement, in each of

which the muscular are curiously like the mental symptoms: delirium tremens in one, an acute noisy and destructive mania in another, chronic alcoholism in a third, and a condition of mental weakness with loss of memory and loss of energy in a fourth.

Writers on gout agree that a suppressed gout may entail mental derangement in some persons; and, on the other hand, that insanity has sometimes disappeared with the appearance of the usual gouty paroxysm. Sydenham noticed and described a species of mania supervening on an epidemic of intermittent fever, which, he remarks, contrary to all other kinds of madness, would not yield to plentiful venesection and purging. Griesinger, again, has directed attention to cases in which, instead of the usual symptoms of ague, the patient has had an intermittent insanity in regular tertian or quartan attacks, and has been cured by quinine. We must bear in mind, however, that intermittence may be a feature of insanity as of other nervous diseases, without ague having any thing whatever to do with it, and without quinine doing any good whatever. Quinine will not cure the intermittence of nervous diseases, though it may cure ague in which the symptoms are intermittent. Griesinger has also pointed out that mental disorder has sometimes occurred in the course of acute rheumatism, the swelling of the joints meanwhile subsiding. These facts, with others which I cannot dwell upon now, prove how important an agency in the production of insanity a perverted state of the blood may be. But it is a mode of causation of which we know so little that I may justly declare we know next to nothing. The observation and classification of mental disorders have been so exclusively psychological that we have not sincerely realized the fact that they illustrate the same pathological principles as other diseases, are produced in the same way, and must be investigated in the same spirit of positive research. Until this be done I see no hope of improvement in our knowledge of them, and no use in multiplying books about them.

It is quite true that when we have referred all the cases of insanity which we can to bodily causes, and grouped them according to their characteristic bodily and mental features, there will remain cases which we cannot refer to any recognizable bodily cause or connect with any definite bodily disease, and which we must be content to describe as idiopathic. The explanation of these cases we shall probably discover ultimately in the influence of the hereditary neurosis and in the peculiarities of individual temperament. It is evident that there are fundamental differences of temperament, and it is furthermore plain that different natures will be differently favored in the struggle of existence; one person will have an advantage over another, and by the operation of the law of Natural Selection there will be a success of the fittest to succeed. It is with the development of mind in the conduct of life as it is with every form of life in its relation to its environment. Life is surrounded by forces that are always tending to destroy it, and with which it may be represented as in a continued warfare: so long as it contends successfully with them, winning from them and constraining them to further its development, it flourishes; but when it can no longer strive, when they succeed in winning from it and increasing at its expense, it begins to decay and die. So it is with mind in the circumstances of its existence: the individual who cannot use circumstances, or accommodate himself successfully to them, and in the one way or the other make them further his development, is controlled and used by them; being weak, he must be miserable, must be a victim; and one way in which his suffering and failure will be manifest will be in insanity. Thus it is that mental trials which serve in the end to strengthen a strong nature break down a weak one which cannot fitly react, and that the efficiency of a moral cause of insanity betrays a conspiracy from within with the unfavorable outward circumstances.

It behooves us to bear distinctly in mind, when we take the moral causes of insanity into consideration, that the men

tal suffering or psychical pain of a sad emotion testifies to actual wear and tear of nerve-element, to disintegration of some kind; it is the exponent of a physical change. What the change is we know not; but we may take it to be beyond question that, when a shock imparted to the mind through the senses causes a violent emotion, it produces a real commotion in the molecules of the brain. It is not that an intangible something flashes inward and mysteriously affects an intangible metaphysical entity; but that an impression made on the sense is conveyed along nervous paths of communication, and produces a definite physical effect in physically-constituted mind-centres; and that the mental effect, which is the exponent of the physical change, may be then transferred by molecular motion to the muscles, thus getting muscular expression, or to the processes of nutrition and secretion, getting expression in modifications of them. When there is a native infirmity or instability of nerveelement, in consequence of bad ancestral influences, the individual will be more liable to, and will suffer more from, such violent mental commotions; the disintegrating change in the nerve-element will be more likely to pass into a disorganization which rest and nutrition cannot repair, not otherwise than as happens with the elements of any other organ under like conditions of excessive stimulation. As physicians, we cannot afford to lose sight of the physical aspects of mental states, if we would truly comprehend the nature of mental disease, and learn to treat it with success. The metaphysician may, for the purposes of speculation, separate mind from body, and evoke the laws of its operation out of the depths of self-consciousness; but the physician-who has to deal practically with the thoughts, feelings, and conduct of men; who has to do with mind, not as an abstract entity concerning which he may be content to speculate, but as a force in Nature, the operations of which he must patiently observe and anxiously labor to influence-must recognize how entirely the integrity of the mental functions de