290 



FERMENTATIONS IN MILK 



Connect with a short piece of rubber tube to a hydrogen 

 generator and pass the gas through the solution for a few 

 minutes : then clamp the rubber connecting tube and disconnect 

 the hydrogen apparatus. 



Dip the open end of the side tube of the flask into a small 



beaker or cylinder con- 

 taining mercury and trans- 

 fer to the incubator at 

 37 C. 



Since the oxygen has been 

 expelled the anaerobic organ- 

 isms can now grow in the 

 medium, and any gas which is 

 produced in the fermentation 

 process can escape by the mer- 

 cury valve without setting up 

 any great internal pressure. 



Examine a drop of the cul- 

 ture after forty-eight hours and 

 note the character of the bac- 

 teria present. 



Test for granulose with iodine 



FK, 47 .-Yeast flask arranged for cultivation in potassium iodide. 



of anaerobic organisms. If Clostridid with Spores are 



present, stain the latter by method given in Ex. 1 2. 



2. Although it is advisable perhaps to limit the term 

 butyric acid fermentation to the production of this acid 

 from carbohydrates, lactic acid, or glycerine, it must be 

 noted that it is a frequent product in the decomposition 

 of proteins by bacteria. 



In the former process butyric acid is one of 

 the chief substances obtained, while, in the latter 

 the amount is usually small and of secondary import- 

 ance. 



