VOLUNTARY MOTION. 477 



senses.* In many animals, a much more general 

 suspension of the actions of life, extending even to 

 the vital functions of respiration and circulation, 

 takes place during the winter months, constituting 

 what is termed Hyhernation. 



Chapter VIII. 



COMPARATIVE PHYSIOLOGY OF THE NERVOUS SYSTEM. 



§ 1 . General view of the Functions of the 

 Nervous System. 



We have seen that the functions exercised by the 

 nervous system are of two kinds, designated re- 

 spectively by the terms reflex,-\ and sensorial. The 

 first consists in transmitting irritations of various 

 kinds, originating in certain parts of the frame, to 

 other parts, where they produce specific actions 

 which are necessary for the due performance of 

 the vital functions, but which are unconnected with 

 either sensation, volition, or even consciousness. 

 The second consists in the transmission of impres- 

 sions made on the organs of sense, which are gene- 

 rally on or near the surface of the body, to certain 

 internal parts connected with the sentient principle, 

 so as to excite sensation, followed by perception, 



* The only indications of dreaming given by the lower animals 

 occur in those possessed of the greatest intellectual powers, such as 

 the Dog, among quadrupeds, and the Parrot, among birds. 



t This term has been introduced by Dr. Marshall Hall, to express 

 the functions of the ganglionic, or as he calls it, the excito-viotory 

 system. 



