TUBERCLE BACILLI IN MILK 1 33 



ooo bacteria per cc. Ripened cream should not contain more than 

 150,000,000 bacteria per cc. and most of which bacteria should be 

 of the lactic acid group. Pathogenic bacteria which may be pres- 

 ent in milk may also be present in the cream. Tubercle bacilli, 

 diphtheria bacilli and typhoid bacilli are the most likely to occur. 

 In the case of doubtful cream, the colon bacillus test should not be 

 omitted and in the case of suspected contamination with patho- 

 genic organisms, the cream, as well as the milk from the same 

 source, should be examined, resorting to the 

 usual animal inoculation tests. 



The tests for the presence of tubercle bac- 

 illi in milk, cream, meats, etc., comprises the 

 microscopic examination of stained (Ziehl- 

 Neelsen method of staining) sediments or con- 

 centrates as may be required, and animal in- 

 oculations. For the animal inoculation test, ^^}^: '^fn"~Iputum^ 

 guinea-pigs are used. CentrifugaHze (in a Stained with carbol- 

 r , 1 ■ \ 1 i c ^^ -11 fuchsin and methy- 



powerful machmej about 250 cc. 01 the milk ieneh\ue.—{Piufield.) 



in order to throw down the tubercle bacilK (with 

 the other inclusions), and from this make the desired cover-slip 

 preparations and inoculate (in the region of the left knee-joint 

 of hind leg) the remainder of the sediment into three healthy 

 guinea-pigs. Place the inoculated guinea-pigs in individual cages 

 and keep them under observation for from 2 to 4 weeks. The 

 reasons why several pigs should be inoculated are as follows. 

 Some of the pigs may be killed by bacteria other than the tu- 

 bercle bacilli and it is always desirable to dupHcate the tests. 

 . At the end of the second week, one of the guinea-pigs should be 

 dissected and the glands of the sublumbar region as well as the 

 glands of the superficial tissues and of the popliteal region exam- 

 ined. If tubercular infection has taken place, these glands will 

 be found much enlarged containing foci of tubercle bacilli. The 

 enlarged glands are dissected and suitable cover-glass prepara- 

 tions made therefrom. If the evidence of tubercular infection 



