38 THE DIASTATIC ENZYME OF SALIVA. [BOOK II. 



More recent The researches of Brown in conjunction with Heron 1 



Browned f an< ^ w ^ ^- orr ^ 2 3 subsequently confirmed and extended 



Heron 1 ' those of Musculus and his co-workers, and have thrown 



additional light upon the complex chemical structure 



of the starch molecule. 



Attempts to separate the Diastatic Enzyme of Saliva. 



The methods employed by Mialhe in his attempts to isolate the 

 diastatic principle of the saliva have been referred to (p. 36). 



Cohnhelm's Subsequently Cohnheim 4 employed the following 



metnod. method : 



The mixed saliva of man is strongly acidulated with phosphoric 

 acid, and lime-water added until the reaction is alkaline and a copious 

 precipitate of Ca 3 PO 4 is obtained. This precipitate carries down all 

 the proteids and all the diastatic ferment which the saliva contains. 

 On treating the precipitate with water, it dissolves the ferment 

 which is precipitated by alcohol in the form of white flocculi, which 

 when dried in vacuo yield a nearly colourless powder containing 

 some alkaline phosphates. From the latter it can be purified by 

 repeated solution in water and precipitation with alcohol. The body 

 at last obtained is nitrogenous ; it is easily soluble in water, and its 

 solution possesses in a marked manner the diastatic power of the 

 original saliva. The solution is said not to exhibit the xantho-proteic 

 reaction*; it is not precipitated by solution of mercuric chloride, 

 platinum tetrachloride, by tannin or by nitric acid, but by neutral 

 and basic lead acetates. 



These reactions appear to shew that the diastatic ferment of 

 the saliva, whatever its exact nature, does not possess the pro- 

 perties of a proteid body. 



Separation In the case of animals whose saliva is endowed with 



of a diastatic amylolytic properties (e.g. the pig), the enzyme may be 

 ferment from extracted from the finely divided salivary glands by 

 the ^salivary digestion in glycerin. From its solution in glycerin 

 glands. the ferment may be precipitated by alcohol, and it may 



afterwards be dissolved in water. 



1 Brown and Heron, 'Contributions to the History of Starch and its Transforma- 

 tions.' Journal of the Chemical Society, 1879 (Transactions), p. 596. 



2 Brown and Morris, ' On the Non-crystallisable products of the action of Diastase 

 upon Starch,' Journal of the Chemical Society, 1885 (Transactions), p. 527. 



3 Brown and Morris, ' The Determination of the Molecular Weight of the Carbo- 

 hydrates,' Journal of the Chemical Society, 1889 (Transactions), p. 462. 



4 Cohnheim, 'Zur Kenntniss der zuckerbildenden Fermente.' Virchow's Archiv, 

 Vol. xxvni. (1865), p. 241. 



