CHAPTER X.

THE MORBID ANATOMY OF MENTAL DERANGEMENT.

BEFORE going on to describe the morbid cerebral changes which have been met with in mental disease some preliminary considerations of a general character will not be amiss, the less so as one is compelled to begin with the acknowledgment that there may be no morbid appearances at all. This absence of discoverable physical changes where marked mental disorder has existed necessarily renders a chapter on morbid anatomy the most barren chapter in a book on mental pathology. A patient dies raving mad, and yet the examination after death shall not perhaps disclose the reason why he was mad or even why he died. To conclude thence, however, that nerve element does not subserve mental function, or is not affected when function is affected, is to make a hasty and unwarranted inference. present we know nothing whatever of the intimate molecular constitution of nerve element and of the mode of its functional action, and it is beyond doubt that important molecular and chemical changes may take place in those inner recesses to which our senses have not gained access. The cerebral nerve-cells are minute laboratories-chemical and physiological—in which not only are the most complex chemical processes in the world carried on unceasingly, but vital processes also which, materialising experiences in structure, condition or determine their intimate constitution. And yet all these processes are hidden from our present means of observation. Where the subtilty of nature so far exceeds the subtilty of human investigation, to conclude from the non-appearance of change to the non-existence thereof

would be just as if the blind man were to maintain that there were no colours, or the deaf man to assert that there was no sound. Justly then may we with Pinel rather doubt the sufficiency of our senses than believe that mental disorder can exist without any physical disorder in the brain, and rest in the certitude that in the fulness of time a means will be discovered to penetrate the yet inscrutable recesses of nerve life, and to make known the physical conditions of its functional manifestations. That it is now a region of uncertainties and obscurities may be taken as promise that it is the destined field of future discoveries.

There are many facts to prove that serious modifications in the constitution of nerve element take place without any other evidence of them than we infer from correlative changes of energy. After severe and prolonged mental exertion there ensues exhaustion, which may be so great that the brain is utterly incapacitated from further function; a large increase of phosphates in the urine bears witness to the disintegration of nerve; the individual is, so far as power of active life is concerned, almost a nonenity; and yet neither microscopist nor morbid anatomist would succeed in discovering any difference between the nerve substance of his brain and the nerve substance of the brain of one who, after due rest and nutrition, was prepared for a day of vigorous activity. The sudden shock of a powerful emotion has produced instantaneous death, just as a stroke of lightning has, and perhaps in the same way; but neither in the one case nor in the other may there be any detectable morbid change. If the electric fish is persistently irritated so as to be made to give forth shock after shock, the excessive expenditure of energy leaves it utterly exhausted, and it can give no more shocks until its powers have been restored by rest and nutrition; its nervous centres have plainly undergone a considerable modification, though we know not the nature of it. Instead of arterial blood send through the brain blood heavily charged with carbonic acid, and the victim of the experiment must inevitably die; but no one can describe the secret change that has been produced in the composition of the nerve element. Without killing a person outright, it is possible, by causing him to breathe a mixture of one part of air and three parts of

carbonic acid, to render him as insensible to pain as if he had inhaled chloroform; but it is the gross result only that is recognisable by our senses. In this regard, however, the experiments of Lister on the early stages of inflammation are of some interest; for he showed that carbonic acid produced a direct sedative effect upon the elements of the tissue, paralysing for the time their vital energies; the effect being transient, and the tissue recovering its energy after a considerable time. The experiment brings us to the individual elements of the tissue, but no farther; it tells us nothing of the more intimate changes that take place in them. It is obvious that the difference may be the difference between life and death, and yet there may be no appreciable physical or chemical change.

As regards morbid appearances in cases of insanity, there can be no question that the instances in which they are not found become less frequent as investigation becomes more searching and efficient; and those who are best capable of judging, and best fitted by acquirements to give an opinion, are those who are most certain of the invariable existence of organic change. When a morbid poison acts on the body with its greatest intensity there are fewer traces of organic alteration of structure met with than in cases where the poison has been milder and has acted more slowly; and so likewise organic change of nerve element in insanity, appreciable by the imperfect means of investigation which we yet possess, may justly be expected only when the degeneration has been going on for a long time. In truth I might not unfitly speak of the morbid changes as (a) ascopic or intramolecular, they being matters of faith, not of observation; (b) microscopic, that is, such as are disclosed by the microscope; and (c) macroscopic, or changes that are visible by the naked eye.

The many careful and important researches into the physiology of nerve which have now been carried on for several years have made it more easy to conceive the existence of undetectable organic changes, albeit they have not revealed their nature. They have been of real service, moreover, in freeing the consideration of the supreme nervous functions from those vague metaphysical conceptions which the notion of mind as

an

exalted spiritual entity and of brain as its humble instrument have reflected upon them, and in making them fit subjects of scientific inquiry by bringing them into the category of organic processes. With the perfecting of present and the discovery of new means of minute investigation, it is probable we may have in time to come an evolution of knowledge of nerve-function not unlike that increased knowledge of the heavens which followed the invention of the telescope.

One of the first things that has been made clear thus far is that time is as essential an element in the intestine motions of nerves as it is in the motions of the heavenly bodies. A definite interval is necessary for the propagation of a stimulus from the peripheric ending of a nerve to its central ending in the brain; and when the stimulus has reached the brain, there is an appreciable interval, about one-tenth of a second, before the will can transmit the message to the nerves of the muscle so as to produce motion. This time-rate of conduction varies in different persons and at different periods in the same person, according to the degree of attention; if the attention be slight, the period is longer and less regular, but if the attention be active, then the period is very regular. But whether the attention be great or little, a certain time must elapse from the moment of irritation of a sensory nerve to the resulting contraction of muscle; and a message from the great toe to the brain will take an appreciably longer time than a message from the ear or face. There is a considerable delay in crossing the spinal cord by the stimulation in a simple reflex action; according to an experiment by Helmholtz, more than twelve times the time required for the transmission of a stimulation through the sensory and motor nerves is required to cross the spinal cord. The time-rate of propagation, again, is greatly dependent upon the temperature of a nerve; cold very much diminishes it, so that the speed may be ten times less in a cold than in a normal nerve; and in a cold-blooded animal, like the frog, the rate is only about 80 feet in a second, while in man it is about 180 feet in the second. Haller first proposed to measure this speed of nervous action, and made a calculation of it in man which was not very far from the truth; but after him no one seems to have attempted

the task, and Müller even pronounced it impossible, because the time seemed to him infinitely little and unmeasurable. In experiments on frogs poisoned with opium or nux vomica, he could not perceive the slightest interval of time between the stimulus applied and the resulting muscular contraction. However, the rate of conduction by nerve has now been found to be not only measurable, but comparatively moderate-not to be compared with the infinitely more rapid motion of electricity and light, less even than the rate at which sound travels, about the same as that of an eagle's flight, and only a little quicker than the speed of a racehorse or of a locomotive. Instead of nervous action being due to the instantaneous passage of some imponderable or psychical principle, conduction by a nerve depends upon a modification of its molecular constitution, for the production. of which a certain time is essentially requisite.

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The attempts which have been made to ascertain the time required by the brain for a volition have shown clearly that it also is a measurable period, and that it differs according as the person is prepared beforehand or not for what he has to voluntarily respond to: thus, for example, Jaager found that when he received an electric shock on one side, knowing beforehand that the shock was to be on that side, the interval between it and the answering signal given by him was about 20th of a second; but if he did not know beforehand on which side the shock was to be, then the interval between shock and respondent signal was about th of a second, that is to say, a difference of th of a second. There can be no question that there is a considerable variation in the time in which the same mental functions are performed by different individuals, in consequence of original constitutional differences, and by the same individual at different times, owing to transitory conditions of the psychical centres. No one who has done intellectual work but knows the vast difference in the rapidity, ease, and success of it according to good or ill moods. "There is," says Locke, "a kind of restiveness in almost every one's mind. Sometimes, without perceiving the cause, it will boggle and stand still, and one cannot get it a step forward; and at another time it will press forward, and there is no holding it in." The oppression of mental