222 CONDITIONS NECESSARY FOR THE ACTION OF TRYPSIN. [BOOK II. 



Kiiiine's first One part of the dried pancreas, prepared as above 

 solution of described, is digested at 40C. for 3 or 4 hours with 5 

 trypsin 1 . ^Q p ar t s of a solution of salicylic acid containing O'l of 



the acid per cent. The mixture is then passed through a linen 

 filter and the filtrate, after it has been allowed to cool, is filtered 

 through paper. If, later on. tyrosiue crystallises out, the process of 

 filtration is again repeated. If the process be successful, a small 

 quantity of the solution should cause a previously warmed flocculus 

 of fibrin to commence to break down in one minute, and should 

 have reduced it to a thin magma in five minutes. 



Kiihne's se- 100 grammes of dried ox pancreas which has been 



cond solution purified by the previously described alcohol- and ether- 

 of trypsin. treatment are digested for twelve hours at 40 C. with 

 500 grammes of a 0'1/ solution of salicylic acid. The mixture is 

 filtered through gauze. The residue is now suspended in 500 c.c. of 

 a 0'25/o solution of sodium hydrate, and thymol having been added, is 

 digested for 12 hours longer. The first salicylic solution is likewise 

 digested for 12 hours after it has been neutralised and rendered 

 alkaline to the same extent with NaOH. 



After filtering and expressing the insoluble matter, both the 

 solutions are united. It was found by Kiihne that of 100 grammes of 

 solid pancreas which had been worked with the undissolved residue, 

 after drying, weighed 12 grammes. It contained the nuclein, the 

 collagen, and the undissolved portion of the elastin of the pancreas. 



SECT. 7. THE CONDITIONS NECESSARY FOR, AND THE PRIMARY 

 PRODUCTS OF TRYPSIN-PROTEOLYSIS. 



The influence ^ was state( ^ ^Y Corvisart that pancreatic juice 



of reaction on could effect the solution of proteids in a medium of 

 the digestive which the reaction might be neutral, alkaline or even 

 activity of % c id. Meissner afterwards pretended that an acid 

 reaction was necessary. Danilewsky, who had worked 

 under Kiihne, stated that fibrin is only dissolved by the pancreatic 

 juice when the solution is neutral or feebly alkaline, a small quantity 

 of alkali hastening the process, a large quantity arresting it. 



The more recent researches of Kiihne have shewn that an alkaline 

 reaction does, in fact, aid the proteolytic action of trypsin, its activity 

 being greatest, cceteris paribus, in solutions containing about 1 per 

 cent, of Na 2 C0 3 . The pancreatic juice itself is a powerfully alkaline 

 solution, and its alkalinity depends upon the above-mentioned salt. 

 There can be no doubt, however, that trypsin besides acting in an 

 alkaline, can also do so in a neutral, medium and in one whose 



1 v. Kiihne, "Verwendung der Verdauung in der Gewebsanalyse," Untersuchungen 

 aus dem physiologisch. Institute der Universitdt Heidelberg, Bd. 1, 1878, Heft n. S. 222. 



