136 THE DIGESTIVE FLUIDS. 



cells, while the pepsin and the same apparently holds good for 

 chymosin is secreted by the adelomorphous cells. The latter are 

 hence also spoken of as pepsin cells, while the delomorphous cells 

 are similarly termed the oxyntic cells of the stomach. 



The existence of a special proteolytic ferment in the pyloric por- 

 tion of the stomach, which has been termed pseudopepsin, and which 

 supposedly resembled trypsin in its action, is doubtful. Abder- 

 halden has shown that tryptic ferments in contradistinction to 

 pepsin are capable of splitting peptids containing an amino-acid 

 which is soluble with difficulty (ty rosin, cystin), such as glycyl-1- 

 tyrosin, and that the ferment of the pyloric region, after activation 

 with hydrochloric acid, is incapable of accomplishing this. 



In addition to the two ferments mentioned, the fat-splitting 

 ferment lipase has also been found in the gastric juice of man and 

 several mammals. (Volhard, Kastle, and Loevenhart.) It is appar- 

 ently furnished by both the pyloric portion and the fundus, but 

 more abundantly so in the latter situation. 



As in the case of the ptyalin of the saliva, it appears that the 

 ferments in question do not exist in the cells as such, but in the 

 form of pro-enzymes or zymogens. These zymogens in the case of 

 pepsin and chymosin are termed propepsin or pepsinogen and 

 prorennin or chymosinogen, respectively. This is apparent from 

 the following facts : 



It has been shown that an extract of the gastric mucosa of a 

 fasting animal when treated with 1 per cent, of soda, and which then 

 has no digestive power whatever, when maintained aseptic with 

 toluol may be kept for months and subsequently be rendered physio- 

 logically active by acidifying with hydrochloric acid to the extent 

 of 0.2 0.3 per cent. If then, however, such artificial gastric juice 

 is alkalinized with soda to the extent of 0.5 per cent., the solu- 

 tion is rendered entirely inactive after a few seconds, when warmed 

 to the temperature of the body, and it is to be noted that the sub- 

 sequent addition of hydrochloric acid is now no longer capable of 

 restoring the activity of the enzyme. This demonstrates, of course, 

 that while the proenzyme is more or less resistent to soda, the fer- 

 ment is thereby rapidly destroyed. On the other hand, it appears 

 that pepsin is more resistant to the influence of carbonic acid than 

 propepsin. Between chymosin and its zymogen similar relations 

 exist. 



Of the chemical nature of the proenzymes and the manner in 

 which they are produced by the cells, practically nothing is known. 

 Nerve-influences, no doubt, are here at work, as in the case of the 

 salivary glands. At the same time the blood-supply is of moment, 

 and we find that during the process of digestion the blood-vessels are 

 dilated, and that the venous circulation is more rapid and the blood 

 of a light-red color. But as in the salivary glands, it is certain that 

 the height of the blood-pressure has only indirectly to do with the 

 activity of the glands. The proenzymes here, as there, are formed 



