778 PHYSIOLOGY OF DIGESTION AND SECRETION. 



of the ash shows that it contains 24 per cent, of potassium, 19 per 

 cent, of sodium, and 0.18 per cent, of calcium. The HC1 amounts 

 to 0.55 per cent. This author states that in one animal during a 

 secretion lasting 3J hours about 5 gm. of chlorin were given off in 

 the secretion in the form of chlorids, an amount about equal to that 

 contained in the entire blood. Carlson,* from his studies upon a 

 human case with a permanent gastric fistula, gives the following 

 figures for the normal secretion: Average specific gravity, 1007; 

 total solids, 0.48 to 0.58 gm. per 100 c.c., of which 0.11 to 0.14 was 

 organic material; total nitrogen, 0.6 gm. per 100 c.c.; ammonia, 

 2 to 3 mgm. per 100 c.c.; amino-acid nitrogen, 3 to 9 mgm. per 100 

 c.c.; average acidity, 0.48 per cent., or, expressed in hydrogen-ion 

 concentration (Menten), a pH of 0.92 to 1.13. Gastric juice does 

 not give a coagulum upon boiling, but the digestive enzymes are 

 thereby destroyed. One of the interesting facts about this secre- 

 tion is the way in which it withstands putrefaction. It may be kept 

 for a long time, for months even, without becoming putrid and with 

 very little change, if any, in its digestive action or in its total acidity. 

 This fact shows that the juice possesses antiseptic properties, and it 

 is usually supposed that the presence of the free acid accounts for 

 this quality. 



The Acid of Gastric Juice. The nature of the free acid in gastric 

 juice was formerly the subject of dispute, some claiming that the 

 acidity is due to HC1, since this acid can be distilled off from the gas- 

 tric juice, others contending that an organic acid, lactic acid, is 

 present in the secretion. All recent experiments tend to prove that 

 the acidity is due to HC1. This fact was first demonstrated satis- 

 factorily by the analyses of Schmidt, who showed that if, in a given 

 specimen of gastric juice, the chlorids were all precipitated by silver 

 nitrate and the total amount of chlorin was determined, more was 

 found than could be held in combination by the bases present in the 

 secretion. Evidently, some of the chlorin must have been present 

 in combination with hydrogen as hydrochloric acid. Confirmatory 

 evidence of one kind or another has since been obtained. The 

 percentage of HC1 in the secretion as it is obtained from an isolated 

 fundic sac of the stomach varies around 0.5 per cent., and we must 

 suppose that this figure represents the concentration of acid in the 

 juice as it is secreted. When the contents of a normal stomach are 

 examined during digestion the acidity is said to be much lower, 

 varying around 0.2 per cent, as a maximum. This low acidity may 

 be accounted for in part by dilution, by neutralization from the al- 

 kaline salts of the saliva or the gastric mucosa, or by combination 

 with the protein of the food, but Boldyreff f states that the acidity 



* For summary consult Carlson, "The Control of Hunger in Health and 

 Disease," Chicago, 1916. 



t Boldyreff, "Quarterly Journal of Exp. Physiol., 8, 1, 1914. 



