OF NATURAL HISTORY. 219 



ufed more liberally by the adtive and laborious than by thofe who 

 lead a ftudious and fedentary life. A great proportion of vegetable 

 food, and particularly of bread, is confidered, by the mofl eminent 

 phyficians, as beft adapted for men who are fond of fcience and lite- 

 rature ; for full meals of animal food load the ftomach, and feldom 

 fail to produce dulnefs, yawning, indolence, and many difeafes 

 which often prove fatal. 



The remainder of this chapter, from unavoidable caufes, muft 

 confift of obfervations of a more defultory kind, ' 



Moft animals, when they live long on a particular fpecies of food, 

 are apt to be affetfted with difeafes, which generally arife from col- 

 tivenefs, or its oppofite. The guiney-pigs, after being confined for 

 fome time to coleworts, contract a loofenefs, which often terminates 

 in death. But, when thofe animals are at full liberty, they prevent 

 this effeft, by an inftindl which teaches them to make frequent 

 changes from moift to dry food : If they are reftrained in their 

 choice, they will eat, as a fuccedaneum, paper, linen, and even wool- 

 len cloths. 



Though fome animals, an3 many vegetables, would be noxious to 

 man, if ufed as food, yet, in general, that matter is more regulated 

 by chance and cuftom than by rational motives. By experience, 

 and the aid of our fenfes, we acquire a tollerable facility of diftin- 

 guifhing falutary from noxious food. Other animals feled: their 

 food inftindively ; and their choice is chiefly determined by the 

 fenfe of fmelling. The fpaniel hunts his prey by the fcent ; but the 

 grey-hound depends principally upon the ufe of his eye. When 

 the grey-hound lofes fight of a hare, he inftantly gives up the chace, 

 and looks keenly around him, but never applies his nofe, in order 

 to difcover the track. Some rapacious animals, as wolves and ra- 



E e 2 vens, 



