Infectiousness of ?l\tilkV- ' i *' \, >''/> I '] \ / 101 



open tuberculosis of the lungs the bacteria get into the milk through 

 the air or straw. 



As early as 1869, prior to the discovery of the tubercle bacil- 

 lus by Koch in 1882, Gerlach proved the infectiousness of milk 

 from highly tuberculous animals through feeding and inoculation 

 experiments. This was also emphasized by Ziirn, Klebs, Sommer, 

 and in 1880 by Bellinger, who first pointed to the fact that the milk 

 of a tuberculous cow in which the udder is not noticeably affected 

 may contain tubercle bacilli. The same results are shown by the 

 works of Stein, Bang, Hirschberger, Ernst, Schroeder and Fiorenti, 

 who succeeded in producing tuberculosis in test animals with milk 

 of tuberculous cattle, even though there was no udder tuberculosis 

 present. Milk from tuberculous udders always has been proved 

 to be especially dangerous (May, Bang). 



If special care were exercised in milking, it not infrequently 

 happens even in extensive, generalized tuberculosis that the in- 

 oculated animals remain well ; thus Nocard from injecting milk of 

 54 cows affected with generalized tuberculosis succeeded only in 

 3 cases in producing inoculation tuberculosis. Therefore it ap- 

 pears that in spite of a generalized tuberculosis when udder tuber- 

 culosis is not present, tubercle bacilli are not always excreted 

 with the milk ; the possibility of elimination however, that is, that 

 the milk of such a tuberculous cow may contain tubercle bacilli, 

 should at all times be given consideration. 



Is milk liable to be affected when tuberculosis cannot be clin- 

 ically demonstrated in suspected cows, or w r hen they appear healthy 

 and yet react to tuberculin? Are tubercle bacilli eliminated only 

 with the milk from animals affected with tuberculosis of the udder, 

 or also in cases where the udder is not affected by tuberculosis? 

 These questions may be answered at the present time with great 

 certainty, namely, that tubercle bacilli of cattle are eliminated with 

 the milk as a rule only in animals which are affected with tubercular 

 mastitis. This question is of especial interest in the eradication of 

 tuberculosis in the dairy herd, since it is well known that calves and 

 hogs are highly susceptible to the tubercle bacillus of cattle. It 

 will be advisable therefore to refer to the more important publica- 

 tions on the elimination of tubercle bacilli with the milk, before 

 entering into the question of the harmfulness of such for man. 



Delepine, Ravenel, Rabinowitsch and Kempner, Gehrmann, Gehrmann and 

 Evans, Moussu and Mohler obtained positive results from milk of animals not clini- 

 cally affected, but reacting to the tuberculin test, through inoculating or feeding of test 

 animals. 



Other investigators, as Martel and Guerin, also Hirschberger, aimed to solve the 

 question by inoculating the milk of slaughtered animals or glandular substance from 

 udders of reacting animals. Their work also frequently gave positive results. All of 

 these authors therefore, conclude with great certainty that tubercle "bacilli may "be 

 eliminated with the milk even from animals which are not clinically affected with tu- 

 berculosis. 



Other views are supported by Archer, Muller, Ostertag, Stenstrom, McWeeney, 

 Pusch and Hessler as the result of their negative findings, namely, if the experiments 

 were conducted under the most painstaking requirements and all contaminations through 



