Neuroscience

“ Indeed, it may truly be said that, alike in anatomy and in physiology, the whole present knowledge of the brain, the spinal cord and the nerves, is in great measure due to the use of experiments on animals. And this knowledge is daily applied to the diagnosis and treatment of diseases and injuries of the central nervous system. “In the case of operations on the brain, you have to form your opinion as to what is going on entirely from your knowledge of the physiology of the brain, and that we owe, of course, in the greatest measure to the discoveries of Hitzig and Fritsch and Ferrier.” ”

“ It is part of a complete nervous system and it is only a part of the brain that is concerned in mental process. A nervous system or something that closely corresponds to it seems to be a necessary acquirement of every living organism that moves freely, and its structure, however complex it may be in its higher development, is built up of a simple arrangement of cells and fibres that receive and transmit movement. Its function is to receive a stimulus and to transmit it to a centre where a responsive movement is prepared. ”

“ I fully admit that any exact account of brain states is at present far beyond our reach; and I am surprised that Professor Ladd should have read into my pages the opinion that psychology as a natural science must aim at an account of brain states exclusively, as the correlates of states of mind. Our mental states are correlated immediately with brain states, it is true; but, more remotely, they are correlated with many other physical events, peripheral nerve currents for example, and the physical stimuli which occasion these. ”

“ The editors are all eminent medical men, who have either acquired distinction through large experience in the treatment of nervous maladies involving intellectual and emotional derangement, or have achieved eminence in the department of experimental physiology of the nervous system. The method is here thoroughly scientific. The brain is not merely something to be recognized, but it is taken as the mary and fundamental object of inquiry—an organ, the properties of which give limits and law to psychology. ”

“ All Mental Process Accompanied by Neural Process.—Whatever the ultimate decision of psychologists may be regarding the relation of mind to the sensory and nervous mechanism of man it is certain that there is so close an association between them that the least alteration in the mechanism means a parallel effect in the mind, or in the words of Huxley, “every psychosis is definitely correlated with a neurosis.” The rind or cortex of gray matter which constitutes the surface of the large cerebral hemispheres of the [Pg 196] human brain is regarded as the seat of consciousness. ”

“ The neurologist to whom a psychological training is truly invaluable, finds himself ill at ease when in his investigations he strikes a problem which has to be studied mainly from a psychological point of view. A piece of tissue, a lump of protoplasm, a nerve cell with its dendrons and axons can be stained, mounted, observed, and experimented upon, but who can get hold of a fact of consciousness, of an elementary psychic state, of a sensation, of a feeling, of an idea, stain them, put them under the microscope for scientific investigation? ”

“ Every impression of sense upon the brain, every current of molecular activity from one to another part of the brain, every cerebral action which passes into muscular movement, leaves behind it some modification of the nerve elements concerned in its function, some after-effect, or, so to speak, memory of itself in them which renders its reproduction an easier matter, the more easy the more often it has been repeated, and makes it impossible to say that, however trivial, it shall not under some circumstances recur. ”

“ It is not even correct to say that thought goes on in the brain. What goes on in the brain is an amazingly complex series of molecular movements, with which thought and feeling are in some unknown way correlated, not as effects or as causes, but as concomitants. So much is clear, but cerebral physiology says nothing about another life. Indeed, why should it? The last place in the world to which I should go for information about a state of things in which 110thought and feeling can exist in the absence of a cerebrum would be cerebral physiology! ”

“ All details aside, the essential fact emerges, as an experimental demonstration, that the intellectual processes—sensation, apperception, volition—are linked irrevocably with the activities of the central nervous tissues, and that these activities, like all other physical processes, have a time element. To that old school of psychologists, who scarcely cared more for the human head than for the heels—being interested only in the mind—such a linking of mind and body as was thus demonstrated was naturally disquieting. ”

“ We may, however, notice here that, as in his nervous organization, no distinctly new parts are discoverable, but only general growth and development, and especially vast increase in the size and working capacity of the cerebrum, together with improved lines of communication between the different parts of the brain, so in the psychical manifestations which this enlarged and better-developed brain exhibits, no faculties are discovered beyond what these various developments in structure render possible. Does man possess intelligence? ”

“ The neurologist traces first the effect of stimuli along the bodily nerves, then integration at nerve centres, and finally the rise of a projective reference beyond the body with a resulting motor efficacy in renewed nervous excitement. In biochemistry, the delicate adjustment of the chemical composition of the parts to the preservation of the whole organism is detected. Thus the mental cognition is seen as the reflective experience of a totality, reporting for itself what it is in itself as one unit occurrence. ”

“ Some refuse to allow that the brain can be the organ of intelligence, from fear of being involved by that admission in materialistic doctrines; while others eagerly and arbitrarily lodge intelligence in a round or fusiform nerve-cell, for fear of being charged with spiritualism. For ourselves, we are not concerned about such fears. Physiology tells us that, except in the difference and the greater complexity of the phenomena, the brain is the organ of intelligence in exactly the same way that the heart is the organ of circulation, and the larynx that of the voice. ”

“ For, as I then observed, in this theory of nerve-fibres becoming more and more functionally developed by use, we probably have a physical explanation, which is as full and complete as such an explanation can ever be, of the genesis of mind. "For from the time that intelligence first dawned upon the scene of life, whenever a new relation had to be established in the region of mind, it could only be so established in virtue of some new line of discharge being excavated through the substance of the brain. ”

“ When nervous movements are transmitted to the cortex of the brain, they not only awaken consciousness, or make the individual aware of something, but the present impression also leaves certain permanent effects in the nervous tissue of the cortex itself. Since, however, cortical activity implies consciousness, the retention of such a tendency within the cortical centres will imply, not an habitual act in the ordinary sense, but a tendency on the part of a conscious experience to repeat itself. ”

“ Every one has long known that, without the brain, intelligence is not possible, but experiment has discovered exactly the part that is played by each portion of the organ. It teaches us that consciousness, or intelligence properly so called, resides in the cerebral lobes, while the lower portions of the brain contain nervous centres destined for organic functions of a lower kind. ”

“ What is the lord of the creation, compared with the antelope for fleetness, or with the elephant and many other animals for strength?
As we ascend the scale of animal life we find a more perfectly developed nervous system; and the relative size of the brain, compared with that of the brute, is found progressively to increase, until it arrives at the [Pg 391] utmost perfection in man. On the system of nerves depends sensation, and there can be no doubt that the more exalted the order of intelligence displayed, the more exquisitely delicate is the nervous system. ”

“ With respect to the organic or physico-chemical conditions of its activity, the brain, then, presents nothing exceptional. If we turn to experiments made upon it by physiologists, we shall find that they have succeeded in analyzing cerebral phenomena in the same way as those of all the other organs. The experimental process usually employed to determine the functions of organs consists in removing them or in destroying them either gradually or suddenly, so as to determine the uses of the organ according to the special disturbances thus caused in vital phenomena. ”

“ Intellect, Emotion, and Volition. Physiologists assign to the cerebrum its functions, and neurological, as well as phrenological writers, have located them as represented in Fig. 68. True, there is no structural division between the parts of the cerebrum to indicate this diversity of function, nor is there any perceptible limit between the sensory and motor filaments of the game nerve. As no one has any reason for denying that separate portions of the brain may manifest distinct functions of the mind, we shall assume it as a conceded proposition. ”

“ In the long process of development of animal organisms out of one another there come to be, it is said, higher and higher degrees of intelligence, as the nervous system becomes more and more capable of complex impressions, until we arrive at the consummate physical organization and the supreme intelligence of the human race. The physical organization is open to our examination, and we find the human brain divided into cerebral masses, with ganglia of sensory nerves extending to the external sensory organs. ”

“ The senses themselves are the rudiments of mind, are the means by which stimuli alighting on sense organs enter consciousness; for the nerves of special sense immediately carry the impetus to the brain, where it is recognized as the “not me,” the something definitely affecting the me, and demanding reaction from the me.
The functions of the cerebrum we find grouping themselves in three classes: intellect, emotion, and volition, more simply, thinking, feeling, and willing; and we find no mental activity of the normal or abnormal mind which will not fall into one of these groupings. ”

“ The brain, as all know, is the seat of ideas, emotions, volition. It is the great central telegraphic station with which many lesser centres are in close relation, from which they receive, and to which they transmit, their messages. The heart has its own little brains, so to speak,—small collections of nervous substance which govern its rhythmical motions under ordinary conditions. But these lesser nervous centres are to a large extent dominated by influences transmitted from certain groups of nerve-cells in the brain and its immediate dependencies. ”

“ Modern mental physiologists differ among themselves as regards the presence of the mind throughout the entire nervous system; some maintaining the view here presented, and others making the brain to be the seat of sensation, and the nerves telegraphic lines, so to speak, for the communication of impressions from the various parts of the body to the brain. ”

“ In the case of the higher functions involving thought, the upper part of the brain, which performs these functions, seems to be a sort of duplex machine, so that we have two brains capable of thinking, just as we have two eyes capable of seeing. It is a remarkable fact that the areas of the brain which are appropriated to the lowest and most instinctive functions, which appear first, lie lowest, and as the functions rise the position of their nerve-centres rises with them. ”

“ What else can be the brain's function in the midst of nature than the transforming of impressions into expressions, stimuli into actions? It is the great apparatus by which the organism steadily adjusts itself to the surroundings. There would be no use whatever biologically in a brain which had connections with the sense organs, but which had no connections with the muscular system, and on the other hand, a brain which had motor nerves and muscular adjustment would be entirely useless if it had not sensory nerves and sense organs connected with it. ”

“ This is the theory which presents great fascination to the student of physical science. By laborious investigation physiology has established the fact beyond the reach of rational dispute, that there is a constant relation of concomitancy between cerebral action and thought. Within experience mind is found in constant and definite association with that highly complex and peculiar disposition of matter called a living brain. The size and elaboration of this peculiar structure throughout the animal kingdom stand in conspicuous proportion to the degree of intelligence displayed ”

“ Brain Complexity.—The most interesting feature of the discoveries in brain anatomy during the past generation, has been that the central nervous system is of even greater complexity than had been thought. Because of this, these new discoveries, instead of solving the biological mystery they subtend, or even helping very much to solve it, have made it still harder to understand just how we succeed in controlling and directing this immensely complex machine, of whose details we are utterly unconscious, yet which we learn to use with such discriminating nicety of adjustment and accomplishment. ”