Effect of Salts and Adds on BiocoUoids and Cell-masses. 53 



condition with sodium bicarbonate. The sodium albuminates which 

 would be formed in the mediiun are highly dissociated, as would be the 

 biocoUoids of the ceU, and both diffusion and hydration would be 

 accelerated. This supposition would be based on the inference that 

 the amphoteric cell-proteins were stronger acids than bases. A further 

 result of the conditions of bacterial action is to be seen in the fact that 

 the growth of bacteria in cultiu-es containing carbohydrates is accom- 

 panied by the production of an acidity which checks their growth and 

 retards their action upon proteinaceous substances present. On the 

 other hand, many molds grow best in relatively high concentrations 

 of acids, the cycle of fermentations in milk furnishing a striking example 

 of the differential action of these organisms.^ The first stage is charac- 

 terized by the action of the lactic-acid-producing bacteria, which con- 

 tinue until their products reach an inhibitory concentration. The 

 soured milk now becomes a suitable medium for Oidium and Penicil- 

 lium, which may thrive in a solution containing as much as 1.25 per 

 cent lactic acid, and continue to grow until the acid is exhausted, and 

 then the neutral or alkaUne solution again becomes a suitable habitat 

 or bacteria. 



^Berman, N., and L. F. Rettger. The influence of carbohydrate on the nitrogen metabolism of 

 bacteria. Jour, of Bacter., 3: 389. 1918. 



