ITS PHYSIOLOGICAL FUNCTION. 53 



stance, sugar, aromatic substances, spirit of wine, and alkalies, 

 when introduced into the stomach, immediately excite an almost 

 overflowing secretion of gastric juice ; while, on the other hand, 

 animal substances, which remain for a longer period in the stomach, 

 require a far greater quantity of gastric juice for their perfect con- 

 version. 



According to my experiments, 100 grammes of the fresh gastric 

 juice of a dog cannot, on an average, effect the solution of more than 

 5 grammes of coagulated albumen (calculated as dry). Now if 

 we assume that an adult man receives into the stomach about 100 

 grammes of albuminous matter in twenty-four hours, there must 

 be secreted 2000 grammes, or 4 pounds of gastric juice, for the 

 digestion of this quantity. As we shall return to this subject in 

 our remarks on the processes of digestion and nutrition, we need 

 not enter into it more fully in the present place. 



After the preceding observations, there can be no doubt re- 

 garding the physiological function of the gastric juice. The gastric 

 juice serves not merely to dissolve, but also to modify the nitro- 

 genous elements of food, as, for instance, the protein-compounds 

 and their derivatives. It was formerly believed that its only use 

 was to convert insoluble and coagulated substances into the cor- 

 responding soluble matters, and thus to render them capable of 

 resorption, and that it did not in any way affect the soluble sub- 

 stances. If we have since convinced ourselves that the casein is 

 first coagulated by the gastric juice, in order again to be converted 

 by it into a soluble substance, we yet believe that soluble albumen 

 neither requires nor undergoes any such alterations in order to be 

 resorbed, or, as we commonly express it, to be assimilated. (Tiede- 

 mann and Gmelin.) On the other hand, we learn, from a positive 

 experimental inquiry, what are the products which are developed 

 during the process of digestion ; and we ascertain that, by the 

 action of natural or artificial gastric juice on protein-bodies or 

 gelatigenous matters, there are formed thoroughly new substances, 

 which, although they coincide in their chemical composition and 

 in many of their physical properties, with the substances from 

 which they are derived, essentially differ from them, not only in 

 their ready solubility (in water, and even in dilute alcohol), but in 

 having now lost the faculty of forming insoluble combinations with 

 most metallic salts. The formation of these substances, which we 

 designate as peptones, depends solely on the action of the gastric 

 juice, and occurs without the evolution or absorption of any gas, 

 and without the production of any secondary substance. 



