PEPTONES. 55 



gave to it the name of albuminose. We shall return, in a future 

 part of the work, to the properties of albumen-peptone. 



The fibrin of the blood is not dissolved by the gastric juice in 

 the same manner as by a solution of nitre (see vol. I. p. 351), but 

 it is converted into a non-coagulable, soluble substance, fibrin- 

 peptone. 



That soluble casein is coagulated in the stomach before it 

 undergoes the actual process of digestion, has been long known ; 

 it being proved by observing milk which has been vomited, and 

 by the well-known property of the calf's stomach (rennet) to 

 induce coagulation. More recent observations have only shown 

 that the casein thus coagulated requires in general a longer time 

 for its solution than most other protein-bodies, and that here also 

 as in the other bodies of this class, the more easy or difficult 

 digestibility principally depends on the atomic grouping in which 

 it is secreted; hence, according to Elsasser,* the casein of 

 woman's milk, which only coagulates into a sort of jelly, is more 

 easily digested than the clotted and more firmly coagulated casein 

 of cow's milk. 



Globulin, vitellin, legumin, and other protein-bodies, behave, 

 according to my experiments, both in natural and artificial diges- 

 tive fluids, precisely the same as albumen. 



It is singular that glutin, chondrin, and gelatigenous tissues, 

 during their digestion in the stomach, are converted into sub- 

 stances which, in their physical and in most of their chemical pro- 

 perties, perfectly correspond with the peptones of the protein- 

 bodies. The degree of the solubility of these substances is how- 

 ever essentially dependant on mechanical relations ; actually 

 formed gelatine is more readily changed than areolar (cellular) 

 tissue, and the latter far more quickly than tendon and cartilage ; 

 indeed, as a general rule, the latter do not remain in the stomach 

 sufficiently long to be completely digested, but for the most part 

 are carried away undigested with the excrements. 



We shall treat of the digestibility of mixed food and of the 

 individual animal tissues, when we consider the digestive process 

 generally. 



Very little attention has hitherto been paid even to the best- 

 known peptones ; indeed, until Mialhe published his researches, 

 positively nothing was known regarding their physical or chemical 

 relations. This chemist erroneously regarded the soluble sub- 

 stances produced by digestion from the protein-bodies and from 

 * Die Magenerweichung der Sauglinge. Stutt. u. Tub. 1846. 



