772 PHYSIOLOGY OF DIGESTION AND SECRETION. 



Analysis of the ash shows that it contains 24 per cent, of potas- 

 sium, 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. The organic 

 portion of the secretion, in addition to the digestive enzymes, 

 consists chiefly of protein. Gastric juice does not give a coagulum 

 upon boiling, but the digestive enzymes are thereby destroyed. 

 One of the interesting facts about this secretion 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 sup- 

 posed 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. It would seem, 

 therefore, that in digestion some of the acid is neutralized by the 

 alkaline salts of the saliva or food, or is combined with the protein 

 material of the food or secretion. Clinicians make a distinction 

 between free and combined acid in the gastric secretion. By the 

 first term is meant that the acid exists in solution as in so much 

 water and is, therefore, largely dissociated with the production of a 

 corresponding amount of hydrogen ions. Under the second term 

 is included the acid that is combined in some way with the protein 

 material. In this form the acid is less dissociated and the acidity, 

 that is to say, the concentration of hydrogen ions, is much less. 

 Methods have been devised for estimating the total acidity and the 



