vii FERMENTS 81 



(p. 54), and probably it or some similar peptonizing or 

 proteolytic ferment effects this change in all organisms 

 which have the power of digesting proteids. Another 

 instance is furnished by diastase, which effects the con- 

 version of starch into grape sugar : it is present in ger- 

 minating barley (see p. 75), and an infinitesimal quantity 

 of it can convert immense quantities of starch. The ptyalin 

 of our own saliva has a like action, and probably some 

 similar diastatic or amylolytic ferment is present in the 

 Mycetozoa which, as we saw (p. 54), are able to digest 

 cooked starch. 1 



1 It has long been suspected that the so-called organised ferments 

 brought about their characteristic changes through the operation of 

 unorganised ferments. In 1897 Buchner obtained such an unorganised 

 ferment, now known as zymase, by vigorous triturition of yeast-cells, 

 under high pressure. W.N.P. 



