The Connection of Body with Mind - Mental Diseases : Part 2

The Story of the Mind
by James Mark Baldwin

(Page 6 of 14)

The lowest, or "third level," includes all the functions which the spinal cord, and its upper termination, called the "medulla," are able to perform alone - that is, without involving necessarily the activity of the nervous centers and brain areas which lie above them. Such "third-level" functions are those of the life-sustaining processes generally: breathing, heart-beat, vasomotor action (securing the circulation of the blood), etc. These are all called Automatic processes. They go regularly on from day to day, being constantly stimulated by the normal changes in the physiological system itself, and having no need of interference from the mind of the individual.

In addition to the automatic functions, there is a second great class of processes which are also managed from the third level; that is, by the discharge of nervous energy from particular parts of the spinal cord. These are the so-called Reflex functions. They include all those responses which the nervous system makes to stimulations from the outside, in which the mind has no alternative or control. They happen whether or no. For example, when an object comes near the eye the lid flies to by reflex. If a tap be made upon the knee while one sits with the legs crossed the foot flies up by reflex. Various reflexes may be brought out in a sleeper by slight stimulations to this or that region of his body. Furthermore, each of the senses has its own set of reflex adjustments to the stimulations which come to it.

The eye accommodates itself in the most delicate way to the intensity of the light, the distance of the object, the degree of elevation, and the angular displacement of what one looks at. The taking of food into the mouth sets up all sorts of reflex movements which do not cease until the food is safely lodged in the stomach, and so on through a series of physiological adaptations which are simply marvelous in their variety and extent. These processes belong to the third level; and it may surprise the uninitiated to know that not only is the mind quite "out of it" so far as these functions are concerned, but that the brain proper is "out of it" also.

Most of these reflexes not only go on when the brain is removed from the skull, but it is an interesting detail that they are generally exaggerated under these conditions. This shows that while the third or lowest level does its own work, it is yet in a sense under the weight - what physiologists call the inhibiting action - of the higher brain masses. It is not allowed to magnify its part too much, nor to work out of its proper time and measure. The nervous apparatus involved in these "third-level" functions may be called the "reflex circuit", the path being from the sense organ up to the center by a "sensory" nerve, and then out by a "motor" nerve to the muscle.

Going upward in the nervous system, we next find a certain group of bodies within the gross mass of the brain, certain centers lying between the hemispheres above and the medulla and spinal cord below, and in direct connection by nervous tracts with both of these. The technical names of the more important of these organs are these: the "corpora striata," or striped bodies, of which there are two, the "optic thalami," also two in number, and the "cerebellum" or little brain, situated behind. These make up what is called the "second level" in the system. They seem to be especially concerned with the life of sensation. When the centers lying above them, the hemispheres, are removed, the animal is still able to see, hear, etc., and still able to carry out his well-knit habits of action in response to what he sees and hears. But that is about all.

A bird treated therefore, for example, these second-level centers being still intact while the hemispheres are removed, retains his normal appearance, being quite able to stand upon his feet, to fly, walk, etc. His reflexes are also unimpaired and his inner physiological processes; but it soon becomes noticeable that his mental operations are limited very largely to sensations. He sees his food as usual, but does not remember its use, and makes no attempt to eat it. He sees other birds, but does not respond to their advances. He seems to have forgotten all his education, to have lost all the meanings of things, to have practically no intelligence. A dog in this condition no longer fears the whip, no longer responds to his name, no longer steals food. On the side of his conduct we find that all the actions which he had learned by training now disappear; the trick dog loses all his tricks. What was called Apperception in the earlier chapter seems to have been taken away with the hemispheres.

Coming to the "first level," the highest of all, both in anatomical position and in the character of the functions over which it presides, we see at once what extraordinary importance it has. It comprises the cortex of the hemispheres, which taken together are called the cerebrum. It consists of the parts which we supposed cut out of the pigeon and dog just mentioned; and when we remember what these animals lose by its removal, we see what the normal animal or man owes to the integrity of this organ. It is above all the organ of mind. If we had to say that the mind as such is located anywhere, we should say in the gray matter of the cortex of the hemispheres of the brain. For although, as we saw, animals without this organ can still see and hear and feel, yet we also saw that they could do little else and could learn to do nothing more. All the higher operations of mind come back only when we think of the animal as having normal brain hemispheres.

Further, we find this organ in some degree duplicating the function of the second-level centers, for fibers go out from these intermediate masses to certain areas of the hemispheres, which reproduce locally the senses of hearing, sight, etc. By these fibers the functions of the senses are "projected" out to the surface of the brain, and the term "projection fibers" is applied to the nerves which make these connections. The hemispheres are not content even with the most important of all functions - the strictly intelligent - but they are jealous, so to spoke, of the simple sensations which the central brain masses are capable of awaking.

And in the very highest animals, probably only monkeys and man, we find that the hemispheres have gone so far with their jealousy as to usurp the function of sensation. This is seen in the singular fact that with a monkey or man the removal of the cortical centers makes the animal permanently blind or deaf, as the case may be, while in the lower animals such removal does not have this result, so long as the "second-level" organs are unimpaired. The brain paths of the functions of the second and first levels taken together constitute the so-called "voluntary circuit".

Copyright 1902 by D. Appleton and Company.

About the Author

James Mark Baldwin (1861-1934) was an American philosopher and psychologist who was educated at Princeton under the supervision of Scottish philosopher James McCosh. He made important contributions to early psychology, psychiatry, and to the theory of evolution.