MENTAL AND SOCIAL EVOLUTION 107 



having a nervous system is controlled by that system. 

 The function of this system is called psychical, to dis- 

 tinguish it from the function of the muscular system, 

 which is termed physical. But there is no real difference 

 in kind. It is one of degree only. The nerve matter is 

 composed of similar cells, which make up the other tis- 

 sues of the body. It will be seen, at 9nce, that if the 

 control of behavior in the animal, is in the function of 

 the nervous system, therefore, the principle of evolution 

 applied to this structure in the same manner, it is ap- 

 plied in the preceding chapter, to the inorganic and or- 

 ganic realms, will show how mind is subject to the same 

 laws of natural selection. It is not necessary to con- 

 sider in detail, in the following pages, the mentality of 

 animals lower than man, except by allusion here and 

 there. Man is seen to be only a family in the order of 

 mammalia, that is, he is classified as an animal. What 

 is peculiar to him in the way of mentality is also char- 

 acteristic of all other animals, in less degree. 



THE NERVOUS SYSTEM. Physiological Psychologists 

 find that the mentality of the human organism 

 is produced by a nervous system, containing about 

 3,000,000,000 nerves, permeating the whole body, hav- 

 ing its external terminations so arranged as to carry 

 with much more rapidity than the other structure of 

 the body can do, certain objective sensations from the 

 outside of the body, and also from those parts of the 

 body, objective to the senses, from within it, that is, 

 from all its objective organs, and functions, to certain 

 internal terminations of this nervous system, called 

 ganglia, or neural centers. The largest ganglion of 

 this system is the encephalon, or central organ, or 

 brain ; and is made up of innumerable strands of 

 nerves, so interwoven, as to appear a solid mass of 



