BOVINE TUBERCm^OSIS. 63 



tubercular complicates the matter of determining whether or 

 not tubercle bacilli are found in milk from a healthy udder. 

 In the light of facts recently brought to attention, the discus- 

 sion of this matter of the udder in its relations to milk inspec- 

 tion is not very profitable. 



The manure of cattle contaminated with tubercle bacilli is 

 regarded as an important source of tubercle bacilli in milk. 

 Reacting tuberculous dairy cows that retain the appearance of 

 health, may actively exi^el tubercle bacilli in the feces (41, 42, 

 43, 46). A very small jiercentage of such ca.ses in a herd could 

 Ijring about a very extensive infection of the milk. Among 

 the possible sources of the bacilli, understood at jiresent, are 

 sputum swallowed, and open tubercular lesions of the intes- 

 tines. Feces constitute the most common contamination of 

 milk as demonstrated by observation of dairy ])ractice, and by 

 the microscopic examination of milk sediments. The i)rescjnce 

 of tubercle bacilli in human feces in early cases has been noted 

 and suggested as a means for the earlv diagnosis of the disease 

 (51). 



l\ibcrcle bacilli in market milk. Anderson (1) found in 

 Washington, D. C, that b.ll'h of 223 samples examined con- 

 tained tubercle bacilli. The results anal\-zed according to the 

 source of the samjiles showed that about 11'/ of the dairicN 

 whose milk was examined showed tubercle bacilli. His meth- 

 ods were such that he believes the results understate the true 

 conditions. 



Schroeder (43) refers to the examination of 350 samples of 

 milk in Washington by different workers with the result that 

 about 5.5'/' showed tubercle bacilli. About one dealer out of 

 every ten was intermittently selling tuberculous milk. Hess 

 (9) examined 107 samples of milk in New York and found 

 tubercle bacilli in 16'/( of the samples. Trask (Ref. 33, Chap. 

 Ill) has collected the results of the work on tubercle bacilli in 

 milk, done by a large number of investigators. 



Human and bovine lypes of iuberclc bacilli. The original 

 ideas of the complete unity of tuberculosis in cattle and in 

 man were based upon the identity- of the lesions in gross and 

 microscopic appearance. Up to 1896, the identity of the 



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