80 Dairy Bacteriology. 



the healthy digestive tract is relatively insusceptible, but 

 with infants and invalids the case is far different. The 

 difficulty of proving an infection in this way is very 

 great, as it is impossible to exclude the more common in- 

 fection by the air; yet a number of well authenticated 

 cases have been traced to this source. The presence of 

 the disease in many cases in the digestive organs alone is 

 inexplicable except in this way. It is impossible to de- 

 termine what percentage of human tuberculosis is ac- 

 quired in this way, but even though the amount be small, 

 it devolves upon us to restrict this possibility in every 

 conceivable way. Not alone should it be considered from 

 the human standpoint, but from the point of view of 

 successful animal industry must every measure be taken 

 to repress and extirpate this disease from our herds. 



Tubercle bacilli in other milk products. If milk con- 

 taining numerous tubercle bacilli is made up into differ- 

 ent products the specific organism still is able to exist in 

 such for a considerable length of time. Heim 1 found 

 that tubercle bacilli were able to live in butter for' a 

 month and in cheese for a fortnight, but the probability 

 of infection occurring in this way is very slight as the 

 quantity of these materials consumed at any one time is 

 not large. 



78. Methods of treating- milk. The possible danger 

 from tuberculosis being spread by a contaminated milk- 

 supply may be greatly diminished or entirely eliminated 

 in the following ways: 



1. Dilution. To produce infection it requires the 

 simultaneous introduction of a number of organisms. 

 Bollinger and Gebhardt 2 showed that milk from tuber- 

 culous animals that would produce the disease in guinea- 



1 Heim, Arb. a. d. kais. Gesundh., 5: 294. 



2 Bollinger, Tagebl. d. 62 Versamm. Deutsch. Naturf., Sept. 1889. 



