NERVOUS SYSTEM. 263 



appears universally to be the main end, the rule, the ordi- 

 nary and natural condition: while pain is but the casualty, 

 the exception, the necessary remedy, which is ever tending 

 to a remoter good, in subordination to a higher law of crea- 

 tion. 



It is a wise and bountiful provision of nature that each of 

 the internal parts of the body has been endowed with a par- 

 ticular sensibility to those impressions which, in the ordina- 

 ry course, have a tendency to injure its structure; while it 

 has, at the same time, been rendered nearly, if not complete- 

 ]}'', insensible to those which are not injurious, or to which 

 it is not likely to be exposed. Tendons and ligaments, for 

 example, are insensible to many causes of mechanical irrita- 

 tion, such as cutting, pricking, and even burning: but the 

 moment they are violently stretched, that being the mode in 

 which they are most liable to be injured, they instantly com- 

 municate a feeling of acute pain. The bones, in like man- 

 ner, scarcely ever communicate pain in the healtliy state, 

 except from the application of a mechanical force which 

 tends to fracture them. 



The system of nerves, comprising those which are de- 

 signed to convey the impressions of touch, is universally 

 present in all classes of animals; and among the lowest or- 

 ders, they appear to constitute the sole medium of commu- 

 nication with the external world. As we rise in the scale 

 of animals, we find the faculties of perception extending to 

 a wider range, and many qualities, depending on the chemi- 

 cal action of bodies, are rendered sensible, more especially 

 those which belong to the substances employed as food. 

 Hence arises the sense of taste, which may be regarded as a 

 new and more refined species of touch. This difference in 

 the nature of the impressions to be conveyed, renders it ne- 

 cessary that the structure of the nerves, or, at least, of those 

 parts of the nerves which are to receive the impression, 

 should be modified and adapted to this particular mode of 

 action. 



As the sphere of perception is enlarged, it is made to 



