AND SSNSAflOtt, &9 



Bfjiain; while, if the cuticle become thickened by 

 hard labour, the impression made on the nerves is 

 proportionally lessened, and little information is con- 

 veyed by them to the mind. 



A due supply of arterial blood is another requi- 

 site for tne action of the nerves of sensation. If 

 they be deprived of this, as by exposing the body to 

 a degree of cold sufficient to drive the blood from 

 the surface, the nerves become almost insensible, 

 and severe wounds may be received in this state 

 without thd individual being conscious of the acci- 

 dent, or feeling the slightest pain. For the same 

 reason, severe cold, after a certain time, ceases to 

 be painful, and death ensues like deep sleep and 

 without suffering. But when a frozen limb is thawed, 

 and the returning circulation begins to set the nerves 

 in action, then suffering commences, and the over- 

 action is in danger of leading to inflammation. The 

 same phenomena, in an inferior degree, must be fa- 

 miliar to every one, in the prickling and tingling so 

 commonly complained of on heating cold hands or 

 feet too rapidly at a good fire, and which arise from 

 the return of the blood stimulating the nerves to 

 undue action. 



It is the nervous tissue of the skin which takes 

 cognizance of the temperature of the bodies by 

 which we are surrounded, and imparts to the mind 

 the sensation of warmth or coldness. In the healthy 

 state, the sensation is a correct index of the real 

 temperature ; but, in disease, we often complain of 

 fold and shivering when the skin is positively 

 warmer than natural. In this way, those whose di- 

 gestion is weak, and whose circulation is feeble, 

 complain habitually of cold, and of cold feet, where 

 others, differently constituted, experience no such 

 sensations. Exercise dissipates this feeling and in- 

 creases heat, by exciting the circulation of the blood, 

 throwing more of it to the surface, and thereby 



