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In the foregoing pages we have had intimations of some of the important questions which arise about the connection of mind with body. The avenues of the senses are the normal approaches to the mind through the body; and, taking advantage of this, experiments are made upon the senses. This gives rise to Experimental Psychology, to which the chapter after this is devoted. Besides this, however, we find the general fact that a normal body must in all cases be present with a normal mind, and this makes it possible to arrange so to manipulate the body that changes may be produced in the mind in other ways than through the regular channels of sense.

For example, we influence the mind when we drink too much tea or coffee, not to mention the greater changes of the same kind which are produced in the mind of the drinker of too much alcohol or other poisonous substances. All the methodical means of procedure by which the psychologist produces effects of this kind by changing the condition or functions of the body within itself belong to Physiological Psychology. So he modifies the respiration, changes the heart beat, stimulates or slows the circulation of the blood, paralyzes the muscles, etc. The ways of procedure may be classified under a few heads, each called a method.

1. Method of Extirpation. - This means simply the cutting away of a part of the body, so that any effect which the loss of the part makes upon the mind may be noted. It is used especially upon the brain. Pieces of the brain, great or small - indeed, practically the whole brain mass - may be removed in many animals without destroying life. Either of the cerebral hemispheres entire, together with large portions of the other, may be taken from the human brain without much effect upon the vital processes, considered as a whole; the actual results being the loss of certain mental functions, such as sight, hearing, power of movement of particular limbs, etc., according to the location of the part which is removed. Many of the facts given below under the heading of Localization were discovered in this way, the guiding principle being that if the loss of a function follows the removal of a certain piece of the brain, then that portion of the brain is directly concerned in the healthy performance of that function.

2. Method of Artificial Stimulation. - As the term indicates, this method proceeds by finding some sort of agent by which the physiological processes may be started artificially; that is, without the usual normal starting of these processes. For example, the physician who stimulates the heart by giving digitalis pursues this method. For psychological purposes this method has also been fruitful in studying the brain, and electricity is the agent customarily used.

The brain is laid bare by removing part of the skull of the animal, and the two electrodes of a battery are placed upon a particular point of the brain whose function it is wished to determine. The current passes out along the nerves which are normally set in action from this particular region, and movements of the muscles follow in certain definite parts and directions. This is an indication of the normal function of the part of the brain which is stimulated.

Besides this method of procedure a new one, also by brain stimulation, has recently been employed. It consists in stimulating a spot of the brain as before, but instead of observing the character of the movement which follows, the observer places galvanometers in connection with various members of the body and observes in which of the galvanometers the current comes out of the animal's body (the galvanometer being a very delicate instrument for indicating the presence of an electric current). In this way it is determined along what pathways and to what organs the ordinary vital stimulation passes from the brain, provided it be granted that the electric current takes the same course.

3. Method of Intoxication, called the "Toxic Method." - The remarks above may suffice for a description of this method. The results of the administration of toxic or poisonous agents upon the mind are so general and serious in their character, as readers of De Quincy know, that very little precise knowledge has been acquired by their use.

4. Method of Degeneration. - This consists in observing the progress of natural or artificially produced disease or damage to the tissues, mainly the nervous tissues, with a view to discovering the directions of pathways and the locations of connected functions. The degeneration or decay following disease or injury follows the path of normal physiological action, and so discloses it to the observer. This method is of importance to psychology as affording a means of locating and following up the course of a brain injury which accompanies this or that mental disease or defect.

Results - Localization of Brain Functions. - The more detailed results of this sort of study, when considered on the side of the nervous organism, may be thrown together under the general head of Localization. The greatest result of all is just the discovery that there is such a thing as localization in the nervous system of the different mental functions of sensation and movement. We find particular parts of the nervous organism contributing each its share, in a more or less independent way, to the whole flow of the mental life; and in cases of injury or removal of this part or that, there is a corresponding impairment of the mind.

First of all, it is found that the nervous system has a certain up-and-down arrangement from the segments of the spinal cord up to the gray matter of the rind or "cortex" of the large masses or hemispheres in the skull, to which the word brain is popularly applied. This up-and-down arrangement shows three so-called "levels" of function. Beginning with the spinal cord, we find the simplest processes, and they grow more complex as we go up toward the brain.

Copyright 1902 by D. Appleton and Company.

Tags: Mental Health

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.