334 STUDIES IN ADVANCED PHYSIOLOGY. 



In the medical field pepsin in some form or other is fre- 

 quently given to supplement the lack of this material in the 

 stomach. In fact, the disease called by the too-general 

 term dyspepsia, is, as the name indicates, frequently inter- 

 preted as a lack of the pepsin. Dyspepsia is, however, a 

 pathological condition of the alimentary canal which is 

 much more frequently not connected directly with the ab- 

 sence or presence of the pepsin, but is due to bacterial fer- 

 mentation set up in the carbohydrates. 



b. Hydrochloric Acid. Gastric juice contains about 

 two parts of free hydrochloric acid in a thousand. This 

 fact is somewhat remarkable, as it is the only mineral acid 

 in the body which occurs in a free condition. It is inter- 

 esting to note in this connection that a certain mollusk of the 

 genus Dolium secretes a salivary juice which contains beside 

 the free hydrochloric acid free sulphuric acid. Of the ex- 

 act manner in which this acid is formed in the stomach we 

 know as yet nothing. There is a good deal of evidence 

 pointing to the oxyntic cells of the stomach as the seat 

 of the production, but the chemistry of it is still missing. 

 The only reasonable explanation is that some of the neu- 

 tral salts, like common salt, which is a combination of 

 sodium and hydrochloric acid, are split into the free acid 

 which then passes into the stomach, and the alkaline base 

 which passes into the blood and which may account for the 

 fact that the blood is normally alkaline even when no alka- 

 line salts are found in the food. 



c. Rennet. In the making of cheese it was long an 

 observed fact that sweet milk could be made to curdle 

 quickly and effectively by adding to the milk a piece of the 

 mucous membrane of a calf's stomach, or of some animal 

 living upon a milky diet. There seems to be in the mucous 

 membrane in question a ferment which has the power to 

 coagulate milk. This ferment is called "rennet" or 

 remain. It has not been possible to get this rennet in a 

 pure form, and so its composition is not known. It is 



