CHAP. III.] SEPARATION OF THE DIASTATIC ENZYME. 209 



treated with magnesium carbonate, with collodion, which carries down 

 with it proteids and the proteolytic ferment in a gelatinous form. 

 The filtrate from this precipitate is concentrated in vacuo and 

 treated with strong alcohol, which throws down a flocculent precipitate. 

 This is digested in a mixture of equal parts of alcohol and water, 

 which dissolves the diastatic ferment, a little tyrosine and some salts, 

 and leaves some albumin undissolved. The liquid is dialyzed, concen- 

 trated in vacuo and precipitated by absolute alcohol. The body thus 

 thrown down possesses in a feeble degree proteolytic properties, due 

 to remaining traces of the proteolytic ferment, but in an intense 

 degree diastatic properties. It does not exhibit proteid reactions, i.e. 

 both the xanthoproteic and Millon's reaction fail. 



coiiiiiieim's Cohnheim obtained from an infusion of pancreas, by 



method 1 . the method which he had already employed in the 



separation of salivary diastase (see p. 38), a ferment which did not 

 manifest proteid reactions, and which was as active as the body which 

 he had prepared from saliva ; it was entirely free from proteolytic 

 action. 



v. Wittich's Finely divided pancreas is dehydrated, first by being 



placed in strong alcohol, and afterwards in absolute 

 alcohol, the action of which should be continued for some time. The 

 Iry solid separated from the alcohol is then macerated in glycerin, 

 glycerin solution is then precipitated with alcohol. The precipi- 

 is dried at a low temperature. It is partially soluble in distilled 

 iter. 



The further purification may be carried on as follows 3 : 



The precipitate produced by alcohol in the first glycerin solution 

 washed with strong spirit, and after partial drying, by the 

 mtaneous evaporation of the spirit, is again treated with glycerin, 

 id this second glycerin extract in its turn precipitated with spirit. 

 There is thus obtained a body soluble in water, possessed of 

 great diastatic power, and, according to v. Wittich, destitute of the 

 proteolytic power. According to this author, when glycerin acts upon 

 pancreas directly, it extracts both the proteolytic and the amylolytic 

 ferments, but when the gland tissue has been first thoroughly dehy- 

 drated only the second of these. Htifner 4 , however, controverted this 

 statement, and by following v. Wittich's method he obtained a body 

 which possessed all three of the ferment actions which are character- 

 istic of the pancreatic juice. It is to be remarked that, according to 

 Kiitme, pure trypsin is not soluble in glycerin, a fact which makes it 



1 Cohnheim, 'Zur Kenntniss der zuckerbildenden Fermente,' Virchow's Archiv, 

 Vol. xxvm. p. 251. 



2 v. Wittich, Pfliiger's Archiv, Vol. n. 

 Liversidge, op. cit., p. 24. 



4 Hufner, ' Untersuchungen iiber die ungeformten Fermente,' Journ. fur prakt. 

 Chemie, N.F., Vol. v., p. 372. 



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