PEPSIN. 4f 



water, and then digested in the cold with about six ounces of 

 distilled water, and repeatedly washed, till a putrid odour began 

 to be developed. The filtered fluid was transparent, viscid, and 

 without any reaction ; it was now precipitated with acetate of 

 lead or corrosive sublimate ; the precipitate was carefully washed 

 and decomposed with sulphuretted hydrogen; the pepsin was then 

 precipitated by alcohol from the watery solution in white flocks. 



The pepsin thus obtained, forms, when dry, a yellow., gummy, 

 slightly hygroscopic mass ; in its moist state it is white and bulky ; 

 it dissolves readily in water, and always retains a little free acid so 

 as to redden litmus ; it is precipitated by alcohol from its watery 

 solution ; mineral acids induce a turbidity in a solution of neu- 

 tralized pepsin, which disappears On the addition of a small excess 

 of the acid ; but if there be a considerable excess of the acid, there 

 is a flocculent deposit; it is only imperfectly precipitated by 

 metallic salts, and not at all by ferrocyanide of potassium ; it has 

 been asserted that pepsin is coagulated by boiling, but Frerichs 

 has shown that the coagulation is merely dependent on its admix- 

 ture with albumen. 



This substance possesses the converting power in so high a 

 degree, that, according to Wasmann, a solution containing only 

 one-sixtieth thousand part, if slightly acidulated, dissolves coagu- 

 lated albumen in six or eight hours. This property of pepsin is 

 not destroyed by alcohol; and in this respect Wasmann and 

 Schwann coincide : it is, however, lost when the solution is boiled 

 or carefully neutralized with potash ; in both cases the fluid 

 becomes turbid. 



Almost simultaneously with Wasmann, similar experiments on 

 the digestive principle were made by Pappenheim* and Valeritin,f 

 and subsequently by Elsasser,| with artificial gastric juice ; and 

 they all arrived at the same general results ; but pepsin sufficiently 

 pure for chemical analysis has never been exhibited up to the 

 present time. 



As in Wasmann's method of procedure, putrid parts and 

 digested particles of food were always mixed with the artificial 

 gastric juice, I struck upon the following method of obtaining 

 a digestive fluid in a state of the greatest possible purity. 



The stomach of a recently-killed pig having been properly 



* Zur Kenntniss der Verdauung. Breslau, 1839. 



t Valentin's Repert. Bd. 1, S. 46. 



1 Magenerweichung der Sauglinge. Stuttgart, 1846. S. 68 ff. 



Ber. d. Gesellsch. der Wiss. zu Leipzig. 1849, S. 10. 



