SYSTEM AJfD GENEBAL SENSATION. 



57 



ganglion, from which nerves proceed to the organs contained in 

 that segment of the animal. T. \V.] 



117. The nerves 

 branch off and diffuse 

 sensibility to every por- 

 tion of the body, and 

 thereby animals are en- 



v 



abled to gain a know- 

 ledge of the general pro- 

 perties of the objects 

 which surround them ; 

 every point of the body 

 being made capable of 

 determining whether an 

 object is hot or cold, dry 

 or moist, hard or soft. 

 There are some parts, 

 however, the ends of the 

 fingers, for example, in 

 which this sensibility is 

 especially acute, and these 

 also receive a larger supply of nerves. 



118. On the contrary, those parts which are destitute of 

 sensibility, such as the feathers of birds, the wool of animals, 

 and the hair of man, are likewise destitute of nerves. But the 

 conclusive proof that sensibility resides in the nerves is, that 

 when the nerve which supplies any member of the body is 

 severed, that member at once becomes insensible. 



119. There are animals in which the faculty of percep- 

 tion is limited to this general sensation ; but their number is 

 small, and, in general, they occupy the lowest place in the 

 series. Most animals, in addition to the general sensibility, 

 are endowed with peculiar organs for certain kinds of percep- 

 tions, which are called the SENSES. These are five in number, 

 namely : sight, hearing, smell, taste, and touch- 



Fig. 36. The Anatomy of Asterias 

 aurantiaca. 



