THE ACID OF GASTRIC JUICE 369 



in aniline colors by the action of hydrochloric acid even in minute traces, 

 whereas lactic and other organic acids have no such action. An aqueous 

 solution of oo-tropeolin, a bright yellow dye, is turned red on the addition of 

 a minute trace of hydrochloric acid, and aqueous solutions of methyl violet 

 and gentian violet are turned blue under the same circumstances. 



The protein matter in the food combines to some extent with the hydro- 

 chloric acid, which then is known as combined acid and does not redden litmus- 

 paper. As this combination is immediate, it follows that no free acid is found 

 in the gastric contents until the amount secreted is more than enough to satu- 

 rate the various albuminous affinities. It is partly for this reason that, as al- 

 ready mentioned, salivary digestion may continue in the stomach for some 

 time after the commencement of gastric digestion. According to Ehrlich, the 

 amount necessary to saturate the affinities of 100 grams of various articles 

 of diet is as follows: 



Beef (boiled) 2.0 grams of pure HC1. 



Mutton (boiled) 1.9 grams of pure HC1. 



Veal (boiled) 2.2 grains of pure HC1. 



Pork (boiled) 1.6 grams of pure HC1. 



Ham (boiled) 1.8 grams of pure HC1. 



Sweetbread (boiled) 0.9 gram of pure HC1. 



Wheat bread 0.3 gram of pure HC1. 



Rye bread 0.5 gram of pure HC1. 



Swiss cheese 2.6 grams of pure HC1. 



Milk (100 c.c.) o .32-0 .42 gram of pure HC1. 



The acid of the gastric juice is not found until after the secretion is poured 

 out on the surface of the mucous membrane of the stomach. Thus Claude 

 Bernard after microscopic examination said that there was no acid in the 

 gastric glands, that "the acid of the gastric juice is formed only after the 

 secretion of the juice, the glands secreting a liquid which breaks up into an 

 acid fluid and another product as yet not definitely determined." Harvey 

 and Bensley, from whom the translation just given is quoted, confirm Ber- 

 nard's views completely. They find by an exhaustive study and by ingenious 

 staining methods for identifying alkalinity and acidity, that the acid of gastric 

 juice does not make its appearance until the secretion reaches the open 

 mouths of the glands and the surface of the mucosa. They observe that 

 in the gland ducts the secretion is viscid, adherent, stainable, and "breaks up 

 into round droplets which maintain their individuality for several minutes," 

 noting "the red reaction also at the same time slowly changing to the blue 

 acid reaction, if the secretion has been stained with cyanamin." "From these 

 observations we are obliged to conclude that the secretion formed in the gland 

 possesses a relatively high content of solids, and that the bulk of the water 

 found in the gastric secretion is added at the level of the glandular foveolae." 

 The parietal cells are alkaline in reaction and not acid, as are in fact all the 

 tissues of the gland. However, the observation is well established that the 



