ACTION OP THE GASTRIC JUICE UPON CASEINE. 261 



the presence of the organic principle is necessary to the di- 

 gestion of this, as well as other nitrogenized alimentary prin- 

 ciples. The action of water containing a small proportion 

 of acid is to render fibrin soft and transparent, frequently 

 giving to the entire liquid a jelly-like consistence. The sub- 

 stance thus produced has been likened by Mialhe to caseine, 

 as it is precipitable by acids and by rennet. The result of 

 the digestion of fibrin in the gastric juice, or in an acidulated 

 fluid to which pepsin has been added, is its complete solution 

 and transformation into a substance which is not affected by 

 heat, acids, or by rennet. 



The substance resulting from the action of. gastric juice 

 upon fibrin, called by Lehmann, fibrin-peptone, presents 

 many points of similarity with the albumen-peptone, but 

 nevertheless has certain distinctive characters. Lehmann, 

 indeed, supposes that there are differences between the prod- 

 ucts of the digestion of all the various nitrogenized aliment- 

 ary principles, sufficiently well marked to distinguish them 

 from each other. 1 



Liquid caseine is immediately coagulated by the gastric 

 juice, by virtue both of the free acid and the organic matter. 

 Kennet, which is so largely used for the coagulation of caseine 

 in the manufacture of cheese, is probably nearly identical with 

 pepsin. Once coagulated, caseine is acted upon in the same 

 way as coagulated albumen. The caseine which is taken as 

 an ingredient of cheese is digested in the same way. Ac- 

 cording to Lehmann, coagulated caseine requires a longer 

 time for its solution in the stomach than most other nitro- 

 genized substances ; and it is stated by the same author, on 

 the authority of Elsasser, that the caseine of human milk, 

 which coagulates only into a sort of jelly, is more easily di- 

 gested than caseine from cow's milk. 2 



The product of the digestion of caseine is a soluble sub- 



1 LEHMANX, Physiological Chemistry, Philadelphia, 1855, rol. i., p. 451 et seq. 

 3 Ibid. 



