220 TRYPSIN. METHOD OF SEPARATION. [BOOK II. 



The earlier attempts to separate the proteolytic enzyme of the 

 pancreas have been already referred to. It has been stated that at 

 first it was believed that the pancreatic juice contained one ferment, 

 which was by most writers termed 'pancreatin' or ' pancreatinin ' 

 possessed of several different actions. 



Through the labours of Danilewsky and Cohnheim, both working 

 under Kuhne's direction, it was, however, clearly made out that the 

 different actions depended upon different enzymes, and attempts were 

 made to separate the diastatic from the proteolytic ferment. The 

 former, it seemed, was neither a proteid nor associated with a proteid 

 body, and the latter also, according to Danilewsky, when in a state of 

 quasi-purity, did not yield the proteid reactions. The subsequent 

 researches of Kiihne appear to shew that Danilewsky fell into error, 

 the proteolytic enzyme being a highly complex body which when 

 decomposed yields proteids and their derivatives. 



Kiihne's me- To infusions or extracts of the pancreas rich in 



tfcod of pre- trypsin, alcohol is added in large excess. The pre- 

 paring trypsin. dpitate (the 'pancreatin' of the earlier experimenters) 

 is dissolved in water at 0C. and precipitated by and digested for 

 some time in absolute alcohol. The precipitate is treated with water, 

 which leaves some albumin undissolved, but which dissolves trypsin 

 and a proteid closely resembling, though not identical with native 

 albumin, and to which Kiihne gives the name of ' Leukoid.' 



From the solution leukoid is precipitated by adding acetic acid 

 until it amounts to 1 per cent. Having thus got rid of the greater 

 part of the leukoid, the liquid is rendered slightly alkaline by means 

 of sodium hydrate, and the precipitate which then falls is filtered off. 

 The solution is concentrated at a temperature of 40 C., when the 

 greater part of the tyrosine which is always present, separates, and 

 to the solution, alcohol is added which throws down the enzyme still 

 contaminated with leukoid, peptones, some tyrosine, &c. From these 

 bodies it is freed by solution in water, dialysis, and precipitation by 

 alcohol, the whole series of processes being repeated several times if 

 necessary. 



1 Etymology of the ivord Trypsin. 



In one of his earlier papers on the proteolytic enzyme of the pancreas, Kiihne 

 announced that he had named this body (the knowledge of which we certainly owe 

 to him) trypsin, without, however, vouchsafing any information as to the etymology 

 of the word. 



The only printed information on the matter occurs as a foot-note to a paper by 

 (a pupil of Kiihne's) Neumeister, " Zur Physiologic der Eiweissresorption und zur Lehre 

 von den Peptonen" (Zeitschr. /. JBiologie, Vol. 27 (1890), p. 345. Neumeister says, 

 referring evidently to what is common knowledge in Heidelberg, "'Trypsin' wird 

 bekanntlich von ep^wrofjiai, zerfalle, abgeleitet, weil dieses Enzym die Eiweisskorper 

 sowohl im mechanischen als auch im chemischen Sinne zum Zerfall bringt." Obviously, 

 however, it must be from the active 0pfarr<a, to break in pieces, that the word is 

 derived. The rendering of the Greek 6 by the t in ' trypsin ' is due to the fact that is 

 always pronounced by Germans as a hard unaspirated T. 



