36 BACTERIOLOGY 



Ammonia Production 



The cultures are made in bouillon in Erlenmeyer flasks. A 

 200 cc. flask is connected with a condenser, in which 100 cc. of 

 the culture is placed, together with 2 g. of calcined magnesia^ 

 Fifty cubic centimetres of distillate are collected in a Nessler jar,, 

 and I cc. of Nessler reagent added. If ammonia is present, the 

 distillate assumes a yellow color, whose depth of shade is pro- 

 portionate to the amount. 



Since bouillon alone, when distilled in the presence of mag- 

 nesia, will with Nessler's reagent give a reaction for ammonia, 

 an equal quantity of plain bouillon should be distilled over 

 at the same time, and its depth of color, when treated with 

 Nessler's reagent, compared with the distillate from the culture. 

 Certain bacteria produce ammonia in bouillon cultures, others- 

 do not. This chemical function is therefore likely to possess, 

 value in differential diagnosis. 



Acid Production in Saccharine Bouillon 



In bouillon containing glucose, lactose, and saccharose, acids, 

 may or may not be generated. The writer's method is to grow 

 the organism for 5 days in ' 2 per cent glucose bouillon. Ten 



cubic centimetres are taken, 50 cc. of water added, and the 



N 

 mixture titrated with — NaOH, using phenolphthalein as an 



indicator. The original titre of the medium being known, the 

 amount of acid produced in the culture can be estimated. The 

 results are expressed in cubic centimetres of normal soda per 

 100 cc. of culture. 



The products of the growth of bacteria in saccharine media 

 may include the following : ethyl alcohol, aldehyde, acetone,, 

 formic, acetic, propionic, butyric, and lactic acids. For the study 

 of these products the following system of analysis is proposed. 



In a litre flask place 500 cc. of bouillon, containing 2 per 

 cent of glucose or lactose. Sterilize, and add 10 g. of sterile 



