Chap. 31.] Digeftible and indigeftible Matters. 325 



bile, the pancreatic juice, altogether or feparately, 

 in no cafe has chyle, or any thing like it, been formed. 



It is not yet afcertained what are the circumftance-s 

 -vhich contribute to render different articles ufed as 

 food, digeftible or indigeftible. Something is un- 

 doubtedly to be afcribed to firmnefs of texture, fince 

 cuticle, horn, hair and feathers, which are indigeftible 

 in their natural ftate, became digeftible and nutritious 

 when reduced to a gelatinous form by Papin's digefter. 

 That the folubility or infolubility of a fwbftance in the 

 ftomach is not, however, merely owing to the degree 

 of folidity, is proved from a circumftance already 

 mentioned, viz. that boiled barley was not acted on 

 by the gaftric juice 'of a buzzard hawk, while pieces of 

 hard beef bone, expofed to its action in the fame man- 

 ner, were completely difiblved. But fubftances may 

 even be rendered too foft $ for a fluid is difficult of 

 digeftion, and its continued ufe very injurious to the 

 ftomach. It may be remarked, that nature has given 

 us very few fluids as articles of food. It therefore 

 feems, that fubftances may be either too compact or 

 too lax in their ftructure, to render them fit fuctjects to 

 be acted on by the dige.ftive powers. 



The degree of cafe, however, with which fubftances 

 are digefted, feems in many cafes owing to a differ- 

 ence in folidity. Brain, liver, mufcle, and tendon 

 are digeftible in the order in which they are here in- 

 ferted. Boiled, roafted, and even putrid meat is eafier 

 of digeftion than raw. Hufks of feeds and the hulls 

 of fruits are indigeftible in their natural ftate, but to 

 what circumftance this is owing is not fully afcer- 

 tained. The whole of our food is fometimes not di- 

 gefted ; this may arife from two caufes, either from 

 fome parts of the food being of too firm a texture to 

 Y 3 be 



