400 LIQUID PARTS OF ANIMALS. 



during chymification, but tried the effect of the gastric juice 

 upon the same kinds of food in phials at the temperature of 1 00, 

 and found it to dissolve them precisely as happened in the sto- 

 mach, though in general after a longer interval of time. 



Dr Beaumont has published the different series of experiments 

 which he made by introducing various articles of food into the 

 stomach, and noticing the time that elapsed before they were di- 

 gested. These experiments throw considerable light upon the 

 relative digestibility of different kinds of food, and on that ac- 

 count are highly deserving the attention of medical practitioners ; 

 but, as they do not throw much light on the nature of the gastric 

 juice, it would be improper to give an account of them here. 



From the preceding account it will be seen, that there is a li- 

 quid secreted in the stomach during digestion, which has the pro- 

 perty of dissolving the food, and reducing it to a kind of pap, in 

 which the various articles of food are so much altered in their 

 appearance that they can no longer be recognized by their sensi- 

 ble properties. We know that during mastication a considera- 

 ble quantity of saliva is mixed with the food in the mouth, and 

 passes along with it into the stomach, so that the gastric juice 

 consists at least in part of saliva. Dr Prout has shown that the 

 gastric juice always contains free muriatic acid, and Tiedemann 

 and Gmelin that in animals which live on vegetables there is 

 always free acetic acid, and occasionally free butyric acid in the 

 stomach. Now it comes to be a question whether the saliva and 

 these acids be not capable of converting all kinds of food into 

 chyme, and therefore do not constitute the whole essential por- 

 tion of the gastric juice. The experiments of Eberle, M tiller, 

 and Schwan have shown that something more is necessary. The 

 following is an epitome of their very curious experiments. 



1. There are certain articles of food that are dissolved in glass 

 tubes by saliva kept at the temperature of 100. This is the case 

 with boiled starch, which, by digestion in saliva, is converted in- 

 to starch-gum and sugar. 



2. There are certain other articles of food which are dissolved 

 in glass tubes filled with water, acidulated with muriatic or ace- 

 tic acid, and kept at the temperature of 100. This is the case 

 with casein, gelatin, and gluten. At least the effects of the dilute 

 acids on these substances agree with what Tiedemann and Gme- 

 lin observed in natural digestion. Gelatin, for example, loses 



