Malic acid 3;^> 



Tartaric acid in 



Citric acid .' 27 



526 



1.5323 grams of finely ground cottonseed meal containing 100 mg. 

 of nitrogen soluble in pepsin solution and 3.03 nig. of nitrogen 

 in form of amides were taken for each trial. The digestive solution 

 was in each case allowed to act on the meal at 40° C. during 30 min- 

 utes. From the total nitrogen dissolved was subtracted the sum of the 

 nitrogen in the pepsin solution used, the amide nitrogen in the cotton- 

 seed meal, and the amount of nitrogen found by test to be dissolved by 

 the pepsin solution without the addition of the acid. The excess of 

 nitrogen dissolved was assumed to be due to the action of the acid in 

 each case, and was taken as the relative measure of that action. The 

 relative action due to added acids, when the amount added was equiv- 

 alent to O.L per cent HCl, was calculated from the separate trials to be 

 as follows : 



Hydrochloric acid 62 Lactic acid 30 



Formic acid 30 



Acetic acid 7 



Propionic acid 1 



Butyric acid 7 



According to these figures lactic, malic, tartaric, citric, and formic 

 acids possess a high value in the digestion of albuminoids. The 

 figures for acetic acid were surprisingly low and those for formic acid 

 unexpectedly high. 



The action of common salt in digestion. — It is known that in the diges- 

 tive process common salt (NaOl) causes a liberal secretion of gastric 

 juice, accelerates the diffusion of the liquids, and in this way aids diges- 

 tion. These experiments were made to determine whether acid pepsin 

 solution containing salt would dissolve a larger amount of albuminoids 

 than a like quantity of pepsin without salt, and if this proved to be the 

 case, whether the salt had a specific action on the pepsin, or on the 

 HOI, or on both. Tests were made of the amount of nitrogen dissolved 

 from 1.5323 grams of finely ground cotton-seed meal (containing 100 

 mg. pepsin-soluble nitrogen) in 30 minutes at 40° C, by each of the 

 following agents : 



(1) Water. 



(2) Water -f NaCl, tliree different solutions (0.25. 0.5, and 1 per cent NaCl). 



(3) Water + HCl, three different solutions (0.05, 0.1, and 0.2 per ceut HCl). 



(4) Water + NaCI + HCl, uiue different solutions (NaCl 0.25, 0.5, and 1 per cent, with 



HCl 0.05, O.l, and 0.2 per cent). 



(5) Acid pepsin solution, 50 c. c, + HCl, three diff'ereut solutions (0.05, 0,1, and 0.2 



HCl). 



(6) Acid pepsin solution, 50 c. c, + NaCl + HCl, uiue different solutions (NaCl 0.25, 



0,5, and 1 per cent, with HCl, 0.05, 0.1, and 0.2 per cent). 



This plan of experiment showed the specific action of salt and hydro- 

 chloric acid, each alone; of hydrochloric acid and pepsin together, of 

 each in connection with KaOl ; and of the three combined. In estimating 

 the action, allowance was made for the nitrogen in the pepsin and in 

 amides, as already described. 



