308 THE SENSORIAL FUNCTIONS. 



ferent parts of the surface. 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 inju- 

 rious : hence the nerves of sensation are distri- 

 buted in less abundance 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 indica- 

 tions of other qualities 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 impressions are all con- 

 veyed 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 sig- 

 nals of alarm on the approach of danger. 



Sensibility to pain must then enter as a ne- 

 cessary constituent among the animal functions ; 



