76 Dairy Bacteriology. 



3. Saprophytic bacteria that can form toxic or poison- 

 ous substances in the milk itself or in the intestine after 

 it is ingested, as in certain types of cholera infantum. 



A. DISEASE BACTERIA DERIVED DIRECTLY FROM AF- 

 FECTED ANIMAL. 



74. Tuberculosis. Of those diseases that are com- 

 municable from the animal to man by means of the milk, 

 tuberculosis is by far the most common. This term is 

 now used to indicate a number of maladies that have 

 heretofore been claimed as separate diseases and which 

 affect warm-blooded animals. It is now known that these 

 different manifestations are all caused by the growth of 

 the tubercle bacillus, which was discovered by Koch in 

 1882. In this connection, reference can only be made to 

 the bovine type of the disease, and the relation that this 

 bears in milk and dairy products to the human race. 

 The disease is caused by the same germ whether it is 

 present in the human being or the lower animals, 1 and 

 the danger of infection exists in the transmission of the 

 virus from one to the other. 



The organism causing this disease is remarkable for 

 the narrow temperature limits within which growth will 

 take place, the minimum being, according to Koch, 86 

 F., while the maximum is 104 F. 



This fact is of importance as it indicates that the tuber- 

 cle bacillus is unable to develop, under normal tempera- 

 ture conditions, in milk after it is drawn. The organism 

 withstands drying readily; in fact, by virtue of this prop- 

 erty, it is most widely disseminated, as the tubercular 

 material is discharged from the diseased animal and is 

 distributed in a dried condition in the dust. 



1 Th. Smith has recently determined that there are certain varietal 

 differences between these two types of tuberculosis. 



