~ TUBERCLE BACILIJ. 153 



expressed for an examination of the milk with respect to the 

 presence or absence of the germs of these diseases. The tech- 

 nical difficulties at present surrounding such work are too 

 great to render it worth undertaking as a matter of routine. 

 Then too it is very likely the germs may not be present at the- 

 time milk is under suspicion, which may be long after the pol- 

 lution of the milk occurred. The presence of diphtheria bacilli 

 in milk has been demonstrated by the inoculation of guinea- 

 pigs with centrifugal sediment and the production of diph- 

 theria. The relation of milk to these diseases as demonstrated 

 by other means is discussed in Chap. III. 



Tubercle bacilli. The examination of milk for tubercle 

 bacilli is not recommended as a profitable line for routine work. 

 Owing to the fact that tubercle bacilli appear in milk inter- 

 mittently, a negative result is of no significance in showing 

 the usual quality of the milk in this regard. Nevertheless, 

 occasions arise when the interest in the result warrants the 

 trouble taken to secure the information as to the presence of 

 the tubercle bacilli. 



The work described below calls for the use of a large centrif- 

 ugal machine instead of the ordinary machine used in urine 

 analysis, but the latter may be employed with the disadvantage 

 of using the smaller amount of milk. The technic- varies 

 somewhat with different w r orkers, but that of Anderson (l) 

 is given here and is also recommended by the A. P. H. A. 

 committee. 



To 50 cc. of well-mixed sample in a sterile centrifuge flask,, 

 add 100 cc. of sterile distilled water. Centrifugalize at 2,000 

 revolutions for one hour. Five cc. of the sediment is inocu- 

 lated into each of at least two guinea-pigs subcutaneously in 

 the abdomen, using a different syringe for each pig. An 

 equal number of control pigs are kept with those inoculated, 

 as a control on health of stock, environment, etc. 



Examine for enlarged glands after four weeks and separate 

 those showing evidence of tuberculosis. Pigs are apt to die 

 early from acute infections resulting from bacteria in the milk 

 other than tubercle bacilli. Those alive at two months are 

 given 2 cc. of crude tuberculin, which kills badly tubercular 



