PEPSIN. 



last precipitate is soluble in ammonia. Salivin is not precipitat- 

 ed by chlorine. 



When salivin is charred, ammonia is given off, and the coal 

 contains potash and soda, 



Salivin from neutral saliva does not act as an alkali, but 

 slightly as an acid. If the saliva be not previously neutralized, 

 reddened litmus-paper, when dipt into it, becomes, blue. The 

 colour of the salivin is yellowish-brown when the alkali of the 

 saliva is not neutralized, and it absorbs moisture from the air. 



CHAPTER VI. 



OF PEPSIN. 



THIS name, (from vwrgig, digestion,) was given by Dr 

 Schwann of Berlin* to a substance which constitutes an essential 

 portion of the gastric juice, as without its action many articles of 

 food could not be converted into chyme in the stomach. All 

 articles of food containing coagulated albumen, fibrin, and (to 

 a certain extent also) casein, f To make an .artificial gastric 

 juice capable of dissolving these substances, the inner coats of 

 the third and fourth stomachs of an ox were digested for twenty- 

 four hours in water containing a mixture of 2 J per cent, of mu- 

 riatic acid of commerce. After this digestion (without heat) the 

 liquor was filtered. It contained in solution 2*75 per cent, of 

 solid matter, and required rather more than 2 per cent, of carbo- 

 nate of potash to neutralize it. When this liquor was digested 

 for several hours on coagulated albumen, (at the temperature of 

 98*,) in powder, it dissolved it completely. 



Muller's experiments showed that the mere acid solution will 

 not dissolve coagulated albumen ; and Eberle and Schwann found 

 that the same acid solution, after the ox's stomach was digested 

 in it, has acquired the property of dissolving albumen. Hence 

 something is taken up from these stomachs which gives the acid 

 liquid the property of dissolving albumen and fibrin. It is to this 

 something that the name of pepsin has been given. 



The following are the facts respecting this principle which 



* Poggendorf's Annalen, xxxviii. 358. 



t The chymosin of Deschamps is obviously the same with pepsin. See Jour, 

 1 Pharm. xxvi. 412. 



