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 hematin 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.” 
MicroscopicM ethod—Some of the sediment obtained by 
centrifugalizing 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- 
