§ 25. Connexion of the Mental Action with the Brain.

From what has been said, we suppose it has been made sufficiently clear, that there is a close and important connexion existing between the mind and the body, and that they are reciprocally the subjects of various influences resulting from this connexion. In what has been hitherto said, however, we have considered the subject in the most general point of view. In other words, we have had no other object than the announcement and establishment of the general fact. We have now to add further, that this doctrine is particularly true as far as the brain is concerned. Without admitting the doctrine that the mind is identical with the brain, or even that the mind finds in the brain a congeries of organs specifically suited to the development of each of its separate faculties, we nevertheless hold it to be certain, not only that there is a reciprocal connexion and influence between the two, but that such connexion and influence exist in a remarkably high degree: so much so that it is absolutely necessary to advert to it in any attempt to explain the mental action, especially disordered mental action.

It may be proper, therefore, to make some general statements in regard to the brain, although we are not left at liberty, by our proposed course of investigation, to enter minutely into that subject.

The brain, although it is susceptible of various subordinate divisions, such as the cerebrum and the cerebellum, may in general terms be described as

that globular mass of nervous matter, which is lodged in and occupies the cavity of the cranium or scull. It is of an irregular figure, exhibiting on its surface a great number of projections and depressions, corresponding in some cases to irregularities in the scull, but which are to be ascribed in part also to convolutions and cavities in the brain itself. The more important divisions of the cerebral mass are, FIRST, into the cerebrum, which occupies the whole of the upper part of the cranium, and the little brain or cerebellum, which in size is about one eighth or ninth part of the cerebrum, and is situated under its posterior lobes; and, SECONDLY, the longitudinal division into two equal and symmetrical halves, termed hemispheres. The spinal cord, or, as it is frequently termed, the spinal marrow, is a cylindrical body of nervous matter proceeding from the lower part of the brain, with which it is connected through the medium of a medullary mass, called the MEDULLA OBLONGATA. Like the brain, it is enclosed in membranes, and is of the same substance. It extends through, and occupies, the vertebral canal. A number of white cords, called nerves, proceed from the base of the brain and from the spinal marrow to different parts of the system. They are composed of medullary matter, and are contained in membraneous sheaths. Some of them communicate with, or, more properly, constitute, at their termination, the different organs of sense.

§ 26. Of the Brain, considered as a part of one great Sensorial Organ.

The nerves, the spinal cord, and the brain, connected together as they are, consisting essentially of the same substance, and contributing, each in its own way and degree, to the same results, may properly be regarded as forming one great SENSORIAL ORGAN. It is by means of the assistance furnished by the sensorial organ (under which expression we include also the subordinate organs of taste, smell, sight, touch, and hearing) that the mind is first brought into action. On this organ, the sensorial, as thus explained, an impression, originating from the presence and application of some external body, must be made, before there can be sensation and external perception, Without the presence of some external body, and without the assistance furnished by the sensorial parts of the system, there is reason to believe that the powers of the mind would never be effectively called into action. It is here, in connexion with this conjunction of body and mind, that we discover the beginnings of mental movement. An impression, for instance, is made on that part of the sensorial organ called the auditory nerve, and a state of mind immediately succeeds which is variously termed, according to the view in which it is contemplated, either the sensation or the perception of sound. An impression is made by the rays of light on that expansion of the optic nerve, which forms what is called the RETINA of the eye, and the intellectual principle is brought into that new posi

tion, which is termed visual perception, or a perception of sight. And the same of other cases.

It will be noticed, that we speak of the new state of mind, the sensation or external perception, as immediately consequent on the application of the outward body to the external senses. But it is necessary to add, in order to have a correct view of the case, that the outward impression is rapidly propagated to the brain (so very rapidly that it may well be considered as a single act) before the mental state results. So that we may properly regard the brain, so far as the mere corporeal process is concerned, as the ultimate seat of sensation. It is there that the bodily impression is felt last. If the impression fails to be felt in the brain, the mental state fails also. Of this there is very easy and satisfactory proof. If, for instance, the nerve, which connects the outward sense with the brain, be divided or be greatly compressed, so as to cut off the communication between them, it is well known that the mind will not be affected by the pressure and application of outward objects as it would otherwise be. In other words, there will be no sensation.

§ 27. Relation of these Views to the General

Subject.

Now we may well inquire whether this view of the connexion existing between the mind and the great sensorial organ, particularly the brain, must not necessarily have an intimate relation to the subject of insanity. Is it possible that this great and important organ can, as a general thing, be disor

dered, or even be disordered merely in some of its parts, without occasioning some degree of disturbance in the mental action? On the contrary, are we not to seek for the origin of a considerable portion of mental disorders in the fact of the disturbed and disordered state of this part of the physical system?

We do not suppose, as we have already had occasion to intimate, that the causes of mental disorder are exclusively physical. There are intellectual and moral causes, as well as those more obvious and, perhaps, more common ones, which are located in the physical structure. Let a man indulge in the frequent exercise of the principle of resentment; let the resentful principle grow stronger and stronger, as it will not fail to do by this indulgence; and ultimately it will exercise an authority inconsistent with the just action of the other parts of the mind; and the person will bear about him, superinduced by mental and not by physical causes, the undoubted marks of insanity. At the same time, we are entirely confident that every system of Disordered Mental Action must be very imperfect which does not recognise distinctly the relation existing between the sensorial organ and the mind, and the important and unquestionable fact that the disordered condition of the former frequently results in a corresponding disordered state of the latter.