GASTRIC JUICE. 401 



its property of gelatinizing and of being precipitated by chlo- 

 rine. 



3. But there are various articles of food which require another 

 digesting principle to convert them into chyme. This is the case 

 with coagulated albumen, fibrin, and (to a certain extent also) 

 casein. To make an artificial gastric juice, capable of dissolv- 

 ing these substances, a portion of the third or fourth stomach of 

 an ox was digested for twenty-four hours in water containing 

 2 f per cent, of muriatic acid, and the liquor was then filtered. 

 It contained in solution 2*75 per cent of solid matter, and re- 

 quired rather more than 2 per cent, of carbonate of potash to 

 neutralize it. When this liquid was digested for several hours 

 on coagulated albumen in powder, it dissolved. 



Muller's experiments showed that the mere acid solution will 

 not dissolve albumen. And Eberle and Schwann found that the 

 same acid solution, after the third or fourth stomach of the ox 

 is digested in it, acquires the property of dissolving albumen. It 

 is clear from this, that something is taking up from these sto- 

 machs, which gives the acid liquor the power of dissolving albu- 

 men and fibrin. To this substance, in consequence of its digest- 

 ing property, Schwann has given the name of pepsin.* 



The gastric juice, it would appear from these experiments, 

 consists of saliva, of muriatic and acetic acids, and of pepsin. 

 This last substance is obtained by digesting the third or fourth 

 stomach of the ox in a dilute solution of muriatic acid. Some 

 experiments were made by Schwann to determine the nature of 

 pepsin. . But they were not very successful. The facts ascer- 

 tained have been stated in a preceding chapter, when treating 

 of pepsin. 



The most characteristic action of pepsin is its precipitating ca- 

 sein or coagulating milk. When 0*42 of pepsin solution is mix- 

 ed with 100 of milk, the milk is coagulated. The quantity of 

 the muriatic acid of commerce necessary to produce the same 

 effect is 3*3 per cent. 



The neutralized solution of pepsin still coagulates milk. But 

 if its temperature be raised to the boiling point its property of 

 coagulating milk is destroyed. 



The small quantity of pepsin which causes the solution of al- 

 bumen is remarkable. Acidulated water holding in solution 



* From vt-^K, digestion. 



C C 



