OF ANIMAL HEAT. 113 



172. This opinion respecting the action of the cuta- 

 neous vessels in exciting, moderating, or almost extin- 

 guishing, our heat, receives much support from the 

 physiological and pathological facts of some parts being 

 frequently of a higher or lower temperature than the 

 rest of the system. 



Thus we must attribute the coldness of the dog's 

 nose to the specific action of its own vessels being 

 modified differently from that of the. rest; so oh the 

 other hand, the burning sometimes of the cheeks and 

 sometimes of the palms of the hands in hectic fever, to 

 the locally increased action of the vessels; besides 

 other phenomena of the same description, v. c. the 

 heat of the genitals during the venereal oestrum, and 

 the obstinate coldness of the feet in certain diseases. 



173. The alimentary canal is the only internal part, 

 besides the lungs, exposed to the contact of the atmos- 

 phere. There is scarcely occasion to prove that it is 

 so exposed, and that we swallow a considerable quan- 

 tity of air. 



The air, when swallowed, is decomposed in the sto- 

 mach and intestines, sO that, during health, it soon 

 loses its elastic form : not, however, when the capil- 

 laries of the canal are debilitated, nor when it exists 

 in too great quantity. 



The immense congeries of blood-vessels in the intes- 

 tines on their internal surface which is usually thought 

 equal to the external surface of the body, agrees very 

 well with this idea. 



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