

PHYSIOLOGY. 175 



the administration of the economy, that the appetite for taking 

 in food is connected with the necessity for it, arising from the 

 wants of the whole system. It is obvious that the appetite is 

 particularly connected with the state of perspiration and the 

 consequent inanition of the vessels on the surface. Exercise 

 increases perspiration, and a sedentary life occasions its going 

 on more slowly. In the same way, exercise a little greater than 

 usual promotes, and a sedentary life diminishes the appetite. 

 Sanctorius has ascertained by experiments, that the appetite is 

 proportionally diminished by causes which dimmish the perspi- 

 ration. But it remains to explain how the perspiration is con- 

 nected with the stomach how in different degrees of emptiness 

 of this organ the appetite will return under exercise, but, 

 though the stomach is empty as usual, will be prevented by 

 causes obstructing the perspiration. We can only say in gener- 

 al, that there certainly exists a particular connexion between 

 the extreme vessels of the surface of the body and those of the 

 stomach itself. We know that a loss of tone in the latter is 

 not only attended by a loss of appetite, but may be productive 

 of vomiting, which is again taken off by restoring the action 

 of the vessels on the surface. We can therefore think of no 

 other connexion than the state of tone of each. The contrac- 

 tion of the cutaneous vessels being increased, the fibres of the 

 stomach will follow the same cause ; and, e contrario, in pro- 

 portion to the emptiness of these extreme vessels, a contrac- 

 tion will be occasioned in them, if they are not distended by 

 fluids moving through them." 



CCIV. Thirst is an appetite for liquids, (" perhaps hunger 

 leads us to take in liquid too, ') which depends upon a sensation 

 chiefly referred to the internal fauces, and arising from the dry- 

 ness or heat of these parts ; from acrimony applied to them, or 

 existing in the fluids poured out there ; from the putrescency 

 or viscidity of the contents of the stomach ; and from all in- 

 creased evacuations. 



" Hunger is a sensation absolutely referred to the stomach, 

 but I say thirst is chiefly referred to the fauces, because I have 

 doubts whether it always arises from a sensation felt there. It 

 may arise from a sensation of the stomach; for every body dis- 

 tinguishes between a dry ness of the mouth, which requires a 



