Page:Popular Science Monthly Volume 81.djvu/172

166 the view that the functions of man's brain and nervous system were specifically different from those of the lower animals. After centuries of hopeless wandering in a labyrinth, investigators at last picked up the ariadnian thread that connects the behavior of the simplest organism with the complex mental life of man, and students have come to realize that in the simpler structure and more easily analyzed functions of ameba, jelly-fish, crab or fish, is to be found the key that will eventually open the book in which we may read intelligently concerning the most complex psychic manifestation.

This change in our point of view is not only of philosophic but of great practical value. The student of the brain is no longer a Sisyphus. Investigators now know that a fact discovered in relation to the nervous system of worm or jelly fish may unlock some of the secrets of the physiology of man's brain. The advance from the study of the simpler reactions of the lower organisms to those of the higher animals is made by easy stages, and the knowledge that the continuity of the chain is unbroken is a source of hope and inspiration. Already the nervous system has been deprived of the mysterious specific properties which once it was supposed to possess. Eminent physiologists tell us that it has only those properties which are found to be distinctively characteristic of protoplasm, the physical basis of life. The capacity for receiving stimuli coming from the external world, of transforming, transferring and storing these impressions is characteristic of living organisms. Plants have the power to pick up and transmit a stimulus. An example of this power is seen in the closure of the leaves of the sensitive plant after being touched. As far as is known, however, plants do not have a differentiated nervous system, but between the various cells of which they are composed there are countless connections probably forming paths for the conduction of impulses. These conditions are not unlike those found in embryos of the higher animals at the time when the movements of heart and body have already begun, but before nerves have developed.

The study of the lowest organisms teaches us that the conductions of nervous impulses occur independently of nerves. More recent studies have led investigators to believe that the nervous system does not in any sense create function, but is to be regarded merely as the great regulator, the transforming apparatus called into existence to assist in preserving the equilibrium of each living organism, amid a play of energies, light, heat, electric waves, etc. As long as the equilibrium is undisturbed we say that the body is in a state of rest, but let that balance be disturbed by any stimulus and a reaction takes place. In comparison with other animals, some of our sense preceptions are very limited as our end organs or receptors are only attuned to pick up waves of certain lengths. Other living organisms, as, for example, many insects,