392 BOARD OF AGRICULTURE. [Pub. Doc. 



Unlike other affections of the mammary gland, tuberculosis 

 does not at once change the appearance and quality of the milk 

 secreted. It is a fact that for months after the disease has 

 appeared in the gland the milk is to all appearances normal, 

 and may be sold and consumed without arousing the least sus- 

 picion. Authorities are, however, not fully agreed as to whether 

 the milk from tubercular cows in which the udder is not involved 

 should be considered dangerous ; but the results of experiment 

 have been positive in a large number of cases where no recog- 

 nizable disease of the udder was manifest. 



Professor Ernst and Dr. Peters, from the result of their ex- 

 periments, conducted under the most exacting conditions and 

 with every possible precaution against contamination, found 

 that the proportion of positive results in a lot of cows affected 

 with a high degree of general tuberculosis was eighty per cent. ; 

 in a lot affected with only a moderate degree, sixty-six per 

 cent. ; and in a lot in which the disease was localized in the 

 lungs, thirty-three per cent. 



The bacilli could only be demonstrated microscopically in one 

 specimen of the milk, showing that inoculation experiments are 

 the most certain guide as to whether the milk is infectious or 

 not. In conclusion Dr. Ernst says : — 



First, and emphatically, that the milk from cows affected with 

 tuberculosis in any part of the body may contain the virus of 

 the disease. 



Second. — That there is no ground for the assertion that 

 there must be a lesion of the udder before the milk can contain 

 the infection of tu])erculosis. 



Third. — That, on the contrary, the bacilli of tuberculosis 

 are present, but with no discoverable udder lesions.* 



In Bulletin No. o of the United States Bureau of Animal 

 Industry (1893) is the report of the inoculation of guinea pigs 

 with milk from six tuberculous cows, where the udder was not 

 visibly diseased, in which positive results were obtained in two 

 cases and negative in four. J. J. McKenzie reports forty per 

 cent, contained bacilli in animals where no lesions could be 

 found in the udder by post-mortem examination. 



Some authorities, however, still contend that the udder is 

 diseased when the milk is infected, but that the disease escapes 



* Many of the preceding examples are collected in Vermont Bulletin No. 42, 



