276 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



revolutions per minute. The milk is diluted with twice 

 its volume of water with the idea that it will decrease the 

 specific gravity of the milk and so permit of the easier 

 sedimentation of the tubercle bacilli. Guinea pigs are 

 then inoculated, subcutaneously in the belly wall, with 5 

 c.c. of the sediment thus obtained. The guinea pigs not 

 dying in at least two months are chloroformed, after 

 being tested with tuberculin, and careful autopsies made. 

 Smears, cultures and sections are made from the various 

 organs of the animals that show any change from the nor- 

 mal. The smears are stained with carbol fuchsin and ex- 

 amined for acid- fast bacilli. 



" Cultures are made on glycerinized potato and glyc- 

 erine agar to rule out Rabinowitch's quick growing acid- 

 fast butter bacillus. 



"Sections are stained with carbol fuchsin for tubercle 

 bacilli and also with haematin and eosin for histological 

 appearances. 



"Tuberculous guinea pigs may be differentiated from 

 nontuberculous by giving sufficient crude tuberculin (2 

 c.c.) subcutaneously to cause the death of the tuberculous 

 animals in twenty- four hours. 



"It is of course understood that the examination of 

 milk for tubercle bacilli is by the very nature of the test 

 limited. For the control of this disease in cattle we must 

 rely upon the tuberculin test." 



MicroscopicMethod Some of the sediment obtained by 

 centrif ugalizing the milk is spread thinly on a glass slide, 

 fixed by heating, stained with carbol fuchsin, decolorized 

 in acid alcohol and counter-stained with methylene blue. 

 If small flakes or clots are present in the milk, one of 

 these is spread on the slide and treated in the same man- 

 ner. The carbol-fuchsin solution is prepared by dissolv- 



