NEKVOTJS SYSTEM. 



j the general development of this system presents little, 

 if any, variation ; but special attributes are coexistent with 

 the development of special organs. The development in 

 this way of particular portions of the nervous system is in 

 accordance with the particular conditions of existence of 

 different animals ; it is a necessary part of their organiza- 

 tion, and is not dependent upon education or intelligence. 

 Examples of this are in the extraordinary development of 

 the sense of sight, hearing, or smell, in different animals. 

 There are animals in which these special senses possess a 

 delicacy of perception to which man, even with the greatest 

 amount of intelligent education, can never attain ; but man, 

 possessing a nervous organization not superior to that of 

 other warm-blooded animals in its general development, 

 and inferior to many in the development of special organs, 

 stands immeasurably above all other beings, by virtue of 

 the immense preponderance of what is known as the en- 

 cephalic portion of the nervous system. 



These brief general considerations will convey some idea 

 of the physiological importance of the nervous system ; of 

 the care which should be exercised in its study ; and of the 

 great interest attached to it, from the fact that the most 

 complex and important of its functions belong to human 

 physiology, and to human physiology alone. 



"We can best define what is to be included under the 

 head of the nervous system, by citing certain of its prominent 

 and well-established properties and functions. 



1. The nervous system is anatomically and physiologi- 

 cally distinct from all other systems and organs in the body. 

 It receives impressions made upon the terminal branches of 

 its sensory portion, it conveys stimulus to parts, determining 

 and regulating the operation of their functions; but its 

 physiological properties are inherent, and it gives to no tis- 

 sue or organ its special " irritability " or the power of per- 

 forming its particular function. 1 



1 We have already discussed the independence of what is called "nervous 



