88 Dairy Bacteriology. 



the milk may become "watery"; but the percentage of 

 animals showing such udder lesions is not large, usually 

 not more than a few per cent. 



On the other hand, in the earlier phases of the disease, 

 where its presence has been recognized solely by the aid of 

 the tuberculin test, before there are any recognizable phys- 

 ical symptoms in any part of the animal, the milk is gener- 

 all} r unaffected. Between these extremes, however, is found 

 a large proportion of cases, concerning which so definite 

 data are not available. The results of investigators on this 

 .point are conflicting and further information is much de- 

 sired. Some have asserted so long as the udder itself shows 

 no lesions that no tubercle bacilli would be present, 1 but 

 the findings of a considerable number of investigators* in- 

 dicate that even when the udder is apparently not diseased 

 the milk may contain the specific organism as revealed by 

 inoculation experiments upon animals. In some cases, 

 however, it has been demonstrated by post-mortem exam- 

 ination that discoverable udder lesions existed that were 

 not recognizable before autopsy was made. In the experi- 

 mental evidence collected, a varying percentage of reacting 

 animals were found that gave positive results; and this 

 number wa? generally sufficient to indicate that the danger 

 of using milk from reacting animals was considerable, even 

 though apparently no disease could be found in the udder. 



The infectiousness of milk can also be proven by the 

 frequent contraction of the disease in other animals, such 

 as calves and pigs which may be fed on the skim milk. The 

 very rapid increase of the disease among the swine of Ger- 



1 Martin, Brit. Med. Journ. 1895, 1:937; Nocard, Les Tuberculoses animates, 1895. 



a Bang. Schmidt's Jahrb., 235:22; Hirschberger, Arch. f. klin. Medicin, 1889; 



Ernst, Infectiousness of Milk, 1895; Ravenel, Bull. 75, Penn. Dept. Agr, 1901. 



