NERVOUS SYSTEM. 331 



intended to be the organs of a delicate touch, are 

 most abundantly supplied with nerves ; each nerve, 

 however, communicating a sensation distinguishable 

 from that of every other, so as to enable the mind 

 to discriminate between them, and refer them to 

 their respective origins in different parts of the sur- 

 face. It is also expedient that the internal organs 

 of the body should have some sensibility ; but it is 

 better that this should be very limited in degree, 

 since the occasions are few in which its exercise 

 would be useful, and many in which it would be 

 positively injurious: hence the nerves of sensation 

 are distributed more sparingly to these organs. 



It is not sufficient that the nerves of touch should 

 communicate the perceptions of the simple pressure 

 or resistance of the bodies in contact with the skin: 

 they should also furnish indications of other qua- 

 lities in those bodies, of which it is important that 

 the mind be apprized; such, for example, as warmth, 

 or coldness. Whether these different kinds of im- 

 pressions are all conveyed by the same nervous 

 fibres it is difficult, and perhaps impossible to 

 determine. 



When these nerves are acted upon in a way 

 which threatens to be injurious to the part im- 

 pressed, or to the system at large, it is also their 

 province to give warning of the impending evil, and 

 to rouse the animal to such exertions as may avert 

 it ; and this is effected by the sensation of pain, 

 which the nerves are commissioned to excite on all 

 these occasions. They act the part of sentinels, 

 placed at the outposts, to give signals of alarm on 

 the approach of danger. , 



Sensibility to pain must then enter as a neces- 



