ACTION OF THE GASTEIC JUICE. 225 



Fibrin, as distinguished from the so-called fibrin of the muscular tissue, 

 or myosine, is not a very important article of food. The action of the gas- 

 tric juice upon it is more rapid and complete than upon albumen. The well 

 known action upon fibrin, of water slightly acidulated with hydrochloric 

 acid, has led some physiologists to assume that the acid is the only con- 

 stituent in the gastric juice necessary to the digestion of this substance ; 

 but observations on the comparative action of acidulated water and of 

 artificial or natural gastric juice show that the presence of the organic 

 matter is necessary to the digestion of this as well as of other nitrogen- 

 ized alimentary substances. The action of water containing a small propor- 

 tion of acid is to render fibrin soft and transparent, frequently giving to 

 the entire mass a jelly-like consistence. The result of the digestion of 

 fibrin in the gastric juice or in an acidulated fluid to which pepsiue 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 fibrin-peptone, resembles albumen- 

 peptone, but nevertheless has certain distinctive characters. 



Liquid caseine is immediately coagulated by the gastric juice, by the 

 action both of the free acid and the organic matter. 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. According to 

 Lehmann, coagulated caseine requires a longer time for its solution in the 

 stomach than most other nitrogenized substances. The caseine of human 

 milk, which coagulates only into a sort of jelly, is more easily digested than 

 caseine from cow's milk (Eliisser). The product of the digestion of caseine 

 is a soluble substance, not coagulable by heat or the acids, called caseine- 

 peptone. 



Gelatine is rapidly dissolved in the gastric juice, when it loses the char- 

 acters by which it is ordinarily recognized, and no longer forms a jelly on 

 cooling. This substance is much more rapidly disposed of than the tissues 

 from which it is formed, and the products of its digestion in the gastric 

 juice resemble the substances resulting from the digestion of the albumi- 

 noids generally. 



Action on Vegetable Nitrogenized Substances. These substances, of which 

 gluten may be taken as the type, undoubtedly are digested chiefly in the 

 stomach. Raw gluten is acted upon very much in the same way as fibrin, 

 and cooked gluten behaves like coagulated albumen. Vegetable articles of 

 food generally contain gluten in greater or less quantity, or substances resem- 

 bling it, as well as various non-nitrogenized matters, and cellulose. The fact 

 that these articles are not easily attacked in any portion of the alimentary 

 canal, unless they have been well comminuted in the mouth, is shown by 

 the passage of grains of corn, beans etc., in the faeces. When properly pre- 

 pared by mastication and insalivation, the action of the gastric juice is to 

 disintegrate them, dissolving out the nitrogenized matters, freeing the starch 

 and other matters so that they may be more easily acted upon in the intes- 

 tines, and leaving the hard, indigestible matters, such as cellulose, to pass 



