208 SEPARATION OF DIASTATIC ENZYME. [BOOK II. 



Now it may be argued that the aqueous extract of the pancreas or 

 of the salivary glands contains no diastatic zymogen for, so far as is 

 known, there is no treatment which will increase its diastatic activity. 

 If we could obtain an extract of the pancreas which when added to 

 starch exerted no effect on it, but which when treated with a little 

 acid and neutralized, or by some similar method, rapidly con- 

 verted starch to sugar, then we should have presumptive evidence 

 of the existence of a diastatic zymogen. From the facts in our pos- 

 session we appear compelled to admit either that a zymogen of the 

 diastatic enzyme does not exist, or if it exists that it differs from the 

 zymogens of analogous ferments by its insolubility in water. 



for believing in The individuality of the diastatic enzyme, and espe- 



the indepen- cially its independence of the one concerning which 



dence of the our knowledge is most definite, viz. trypsin, is proved 



diastatic en- ^ ^ Q following considerations : 



1. A pancreatic extract, or pancreatic juice, may be obtained, 

 which is rich in the diastatic ferment and contains no proteolytic 

 ferment. This, as already previously stated, is often the case with 

 the secretion obtained from so-called permanent pancreatic fistulse. 



2. In different animals not only the absolute but the relative 

 richness in diastatic and proteolytic enzymes differs. Thus Roberts, 

 as we have already stated, found that the diastatic activity of the pig's 

 pancreas is more than ten times as great as that of the sheep. The 

 proteolytic activity of the pancreas of the sheep is, on the other hand, 

 considerably greater than that of the pig. 



3. As will be pointed out in the sequel, although attempts to 

 obtain the pure ferments have hitherto not been successful, methods 

 are known by which one ferment may be obtained absolutely free 

 from the others. 



Attempts to isolate the Diastatic Ferment. 



First experi- -^ was Bouchardat and Sandras who first attempted 



ments of Bou- to separate the agent which conferred upon the 

 chardat and pancreatic juice the property which they had dis- 

 Sandras. covered, of converting starch into sugar. They treated 



infusions of pancreas with water, and precipitated the solution with 

 alcohol. The precipitate they found to be again soluble in water 

 and to possess powerful diastatic action. They termed it pancrea- 

 tine. The body thus precipitated must, however, as we know, have 

 consisted of a mixture of the several pancreatic ferments. 



Daniiewski's The first to attempt to separate the diastatic 

 method 1 . ferment was Danilewski. The principle of his method 



was to precipitate aqueous infusions of pancreas, which had been 



1 Danilewski, ' Ueber specifisch wirkende Korper des natiirlichen und kiinstlichen 

 pancreatischen Saftes,' Virchow's Archiv, Vol. xxv. p. 279. 



