512 Tuberculosis. 



In tuberculosis of the udder the milk is always infected, 

 sometimes to such an extent that 0.00001 g. of milk when in- 

 jected intraperitoneally into a guinea pig will produce a fatal 

 tuberculosis (Ostertag). Further, the milk from infected cows 

 which already show clinical symptoms of disease, may contain 

 tubercle bacilli even though the udder is apparently perfectly 

 healthy; since small tuberculous foci in the glandular tissue 

 could not of course be recognized by clinical examination. Re- 

 cent experiments have shown that cows in apparently perfect 

 health which reacted to the tuberculin test may discharge 

 tubercle bacilli with the milk. In such cases, of course, in the 

 face of all negative clinical evidence, the mammary tissue may 

 contain minute metastatic tuberculous foci; furthermore the 

 possibility cannot be refuted that tubercle bacilli may occa- 

 sionally gain entrance into the circulation from tuberculous foci, 

 be carried into the mammary glands and in this way pass into 

 the milk. 



The infectiousness of milk from a tuberculous cow has frequently- 

 been demonstrated since the time of Gerlaeh (1869). Aside from the 

 product of evidently diseased udders, in which case the milk almost 

 invariably contained tubercle bacilli in large numbers, Hirschberger 

 succeeded in producing tuberculosis in guinea pigs with milk from 

 clinically diseased cows with apparently healthy udders, by means of 

 intraperitoneal injection in 11 eases out of 20, Ernst in 26.8% out of 

 33 cases,. Nocard 3 times in 54 eases. 



As far as the use of milk is concerned coming from apparently 

 healthy cows which have reacted to the tuberculin test, the results of 

 experiments vary. 



Ostertag was the first to conduct exact experiments to shed light upon this 

 subject. The milk from 49 reacting cows was collected in separate containers 

 with observance of every possible precaution, and injected intraperitoneally into 

 guinea pigs. The results show that not a single sample of milk contained tubercle 

 bacilli. On the other hand 14 inoculations of guinea pigs made from a mixture 

 of the above 49 samples produced tuberculous disease in one guinea pig. Feeding 

 experiments with this milk produced no positive infections. In a second experiment 

 the milk of 18 cows was used. In this case neither intraperitoneal injections into 

 guinea pigs, nor the feeding of the milk for several months to guinea pigs, swine 

 and calves produced tuberculosis. Similar results were obtained by Miiller and 

 Aseher who used the milk of 9 and 7 reacting cows, respectively, in experiments 

 with guinea pigs. From this Ostertag concluded that milk from merely reacting 

 cows contained no tubercle bacilli. 



Bacteriological examination of milk of 5 head by MacWeeny and of 50 

 head of cattle by Stenstrbm, some of which were clinically diseased, others affected 

 with latent tuberculosis but with healthy udders gave similar negative results. 

 Hessler obtained the same results with 61 merely reacting cows. Schroeder & 

 Cotton also are of the opinion that tubercle bacilli are' excreted with the milk 

 only where the udder itself is diseased. Of 11 cows, 9 of which had generalized 

 tuberculosis and 2 advanced pulmonary tuberculosis, the milk proved virulent by 

 inoculation in 1.78% and by feeding in 0.68% of cases. These results might of 

 course have been due to subsequent infection of the milk. 



On the other hand Gehrman & Evans found the milk virulent in 9 out of 

 41 reacting cows in spite of the fact that a post-mortem failed to reveal tuberculous 

 lesions either in the udder or in other internal organs. In 2 cows there were only 

 slight lesions in a few lymph glands. Eavenel demonstrated the infectiousness 

 of milk of 5 reacting cows none of which showed tuberculous lesions at post-mortem 

 examination. Mohler, of Washington, examined the milk of 56 reacting cows only 

 9 of which showed symptoms of tuberculosis after months of observation, and in 

 all cases the udder was perfectly normal. In 8 of the cows the milk proved to be 



