CHAPTER III 



THE EVOLUTION OF THE NERVOUS SYSTEM OF 



MAN 



GEORGE HOWARD PARKER 



PROFESSOR OF ZOOLOGY, HARVARD UNIVERSITY 



The body of man, like that of the other higher animals, 

 carries a full complement of organs. These organs are usually 

 arranged by anatomists under some ten heads, the so-called 

 organ systems, and are familiar to you as the skeleton, the 

 muscular system, the circulatory system, the nervous system, 

 and so forth. Although physicians have been telling us that 

 we normally live so long as our blood vessels last, it is never- 

 theless true that our daily life is dependent not upon a single 

 system of organs strictly but upon the interaction of all the 

 systems that we possess. No one system can be eliminated 

 without serious consequences. True we may have our tonsils 

 taken out, our appendix removed, we may lose an arm or a leg, 

 a kidney, or even a lung, but no one will give up with impunity 

 both kidneys, or both lungs, or shed his whole digestive tract. 

 Death would be the inevitable and immediate result. Our 

 systems of organs are so interrelated that they form a unified 

 whole which justifies the biological conception of an organic 

 individual. The integrity and continued existence of such an 

 individual is dependent upon the presence of at least the essen- 

 tial members of each system. Thus the organism as a whole, 

 to use a current expression, is more than an assemblage of 

 parts; it is an integrated unit. 



