162 PROTAGON. 



the filtrate with lime-water. Collect the precipitate on 

 a filter, wash and treat with dilute hydrochloric acid. 

 Treat the clear solution with lime-water, collect the 

 precipitate, dissolve in dilute hydrochloric acid, and add, 

 through a thistle funnel reaching to the bottom of the 

 solution a saturated solution of cholesterine in a mix- 

 ture of one part ether and four alcohol, and shake the 

 whole well. Filter off the precipitate which consists 

 of cholesterine and pepsine, wash, and finally shake up 

 in a bottle with ether; allow to stand, remove the 

 ethereal solution of cholesterine with a syphon and 

 filter the remaining liquid. The filtrate will consist of 

 a solution of pepsine. 



2. Acidify this solution feebly with hydrochloric acid, 

 add to the solution thus acidified some albumen ; it 

 will rapidly be dissolved. 



3. Add to the solution tannic or mercuric chloride ; 

 no precipitate is formed. 



Protagon (Liebreich). 1. The brain of an animal 

 just killed is freed from blood by injecting water till it 

 issues colourless. The substance is then comminuted, 

 shaken with repeated quantities of water and ether (to 

 remove cholesterine and matters soluble in water), and 

 the residue digested with warm (45 C.) 85% alcohol. 

 The alcoholic extract on cooling deposits a flaky 

 precipitate, which must be exhausted with cold ether, 

 and purified by recrystallising from warm alcohol. 

 Pure protagon has the following properties. 



2. Light flocculent powder, consisting under the 

 microscope of radiated needles, little soluble in cold, 



