68 Dairy Bacteriology. 



scopic and animal experiments, but it is also abun- 

 dantly confirmed by the frequent contraction of the 

 disease by calves and hogs when fed on factory by- 

 products. This latter class of animals is particularly 

 dangerous, because there is no way in which the dan- 

 ger can be recognized. 



FIG. 17. A TUBERCULOUS ANIMAL. 



The animal appears perfectly healthy although she has had 

 the disease for five years. 



It has also been proven that milk may become in- 

 fected through the feces. In coughing up material from 

 the lungs and associated glands, the matter is swal- 

 lowed, instead of expectorated, as in man. The organ- 

 isms retain their vitality in the intestine, and are voided 

 in the feces. Under ordinary conditions, the flanks 

 and udder become more' or less polluted with such filth, 

 and the evidence is conclusive that infection of milk is 

 not infrequently occasioned in this way. The fact that 



