70 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



seems to paralyze the smaller blood vessels, which then 

 enlarge, become gorged with blood, and the part becomes 

 finally hot and inflamed. Stimulation of these nerves, 

 on the contrary, produces contraction of these blood 

 vessels and coolness and paleness of the part. Blushing, 

 on the one hand, and the paleness of terror, on the other, 

 are supposed to arise from opposite conditions of the 

 vasomotor nerves. 



Illustration by Telegraphy. — If we must push the tele- 

 graphic illustration to include this system also, then it 

 may be compared to a municipal government control- 

 ling local affairs. 



SECTION V. 



COMPARATIVE PHYSIOLOGY AND MORPHOLOGY OF THE 

 NERVOUS SYSTEM. 



Introductory — Outline of the Classification of Animals. 



About to enter now on the comparative morphology 

 and physiology of the nervous system, it becomes neces- 

 sary to have in mind some scheme of classification of 

 the animal kingdom. A true classification is a compen- 

 dious expression of perfect knowledge, and would seem 

 therefore to come last of all. But some provisional 

 classification is a necessary condition of increase of 

 knowledge, because it is impossible to deal scientifically 

 with animals except in groups. Therefore our plan 

 will be to give a simple outline of such a classification 

 and to verify it or modify it as we proceed. There are 

 a great variety of classifications which have been pro- 

 posed, almost as many as the proposers. We select one 

 which is probably as good as any, and has, moreover, 

 the additional advantage of comparative simplicity, for 

 our main object is to be able to handle the material. 



