188 life's beginning on the earth 



relays or ganglia, as they are called. In this manner a 

 separate division of the nervous system is formed, which 

 although not subject to our will, depends upon the general 

 condition of the brain, the state of emotion, and on nu- 

 merous other highly involved factors. 



The following statement taken from Dr. Alexis Carrel's 

 recent book, Man the Unknown, eloquently describes the 

 stupendous complexity of the brain: "Our intelligence can 

 no more realize the immensity of the brain than the extent 

 of the sidereal universe. The cerebral substance contains 

 more than twelve thousand millions of cells. These cells 

 are connected with one another by fibrils, and each fibril 

 possesses several branches. By means of these fibrils, they 

 associate several trillions of times. And this prodigious 

 crowd of tiny individuals and invisible fibrils, despite its 

 undreamed-of complexity, works as if it were essentially 

 one." 1 



It would perhaps take more than a lifetime to describe 

 all the details of the nervous system. The task of grasping- 

 its purpose and the mode of its functioning presents still 

 greater difficulties. But no one dares even to guess at 

 present how such a stupendously complex piece of machin- 

 ery could have developed from the ocean-born self-regener- 

 ating enzymes or the primitive first cells which came from 

 them. No one can explain at present how matter came to 

 possess the faculty of organizing itself in such a manner. 

 And yet this problem is the real aim and ultimate goal of 

 scientific research. Some day in a remote future science 

 will be prepared to attack it. 



8. THE NATURE OF THE NERVE IMPULSE 



In a thousand different ways nature performs its mar- 

 velous work in t he living world. We are slow to recognize 



1 Quoted with the special permission of the publishers, Harper & Broth- 

 ers, of New York. 



