THE EFFECTS OF BACTERIA. 123 



tenuis transforms amygdalin into benzaldehyd, but 

 this function cannot be separated from cell life. 



Eennet ferments i.e.. bodies which coagulate milk 

 of a neutral (or amphoteric) reaction and indepen- 

 dently of the action of acids are not wanting among 

 the bacteria. It can be demonstrated, for example, 

 in not too old cultures of bacterium prodigiosum 

 which, sterilized at 55-60 } can easily coagulate 

 sterilized milk solid in one or more days (Gorini : C. 

 B.; XIL, 666). 



So far as I know, thorough investigations concern- 

 ing the distribution of this ferment are still lacking. 

 We may suspect it in all varieties which coagulate 

 milk without possessing the power of forming lactic 

 acid out of milk sugar. 



II. THE CHEMICAL ACTIONS OF BACTEEIAL 

 METABOLISM. 



Like the production of ferments, the majority of 

 the other chemical actions of bacteria depend, in 

 great measure, on the nutrient medium. This is 

 most striking when the growth of many forms of 

 bacteria is observed upon an albuminous nutrient 

 medium, which at one time is free from sugar, at 

 another time contains sugar. In the former event, 

 apart from pigment substances and perhaps some 

 badly smelling substances, hardly any perceptible 

 metabolic products are formed , but in the latter event 

 there is often a very striking change, characterized 

 by the development of gas and active production of 

 acid. The organism produces fermentation in the 

 sugar-containing medium, in the other it does not. 



