84 BACTERIOIvOGICAL EXAMINATION OF MILK. 



COCCUS Marpmann; Sphaerococcus Marpmann; and 

 Streptococcus acidi lactici Grotenfeld. The difference 

 between the individual species lies chiefly in their physi- 

 ology. For example, Bacillus acidi lactici Hueppe, pro- 

 duces lactic acid and carbonic acid, and the Bacillus acidi 

 lactici Leichmann, lactic acid and ethyl alcohol, etc. 



IV. DEMONSTRATION OF INDIVIDUAL PATHO- 

 GENIC BACTERIA IN MILK. 



I. BACILLUS TUBERCULOSIS. 



Sometimes the cover-glass preparation is successful in 

 demonstrating the bacteria. For the preparation of such, 

 different directions are given. 



(fl) ' Method of Ahrens: A drop of milk is placed 

 upon the cover-glass with a drop of sterilized water. 

 This is dried in the air and fixed by slightly warming. 

 The cover-glass is then placed in a mixture of 3 drops 

 of a concentrated alcoholic solution of fuchsin and 3-4 

 c. c. of chloroform. After ten minutes it is transferred 

 to 4-6 c. c. of 96 per cent alcohol, to which has been 

 added 2-3 drops of diluted sulphuric acid. After wash- 

 ing in water it is double-stained with an aqueous solu- 

 tion of methylene blue. 



(5) Method of Alessi: A drop of milk is dried 

 upon the cover-glass by moderate warming and 2-3 drops 

 of one per cent sodium hydroxide solution added. It is 

 again warmed until saponification of the fat takes place 

 (three or four minutes), washed with water and stained 

 as usual, for example, according to Gabbet ; 2 minutes in 

 cold carbolic fuchsin, 50 seconds in cold sulphuric acid 

 methylene blue Gabbet, i. e., methylene blue 2 parts, 25 

 per cent H2SO4, 100 parts. 



{c) Method of Schrank: A drop of diluted 

 milk is dried in the air on a cover glass. The 

 casein is fixed by placing the cover-glass on a copper 



