INFECTIOUS DISEASES OF CATTLE. 421 



Concerning the infectious nature of milk secreted by tuberculous 

 cows, authorities have universally agreed that when the udder itself 

 is in the slightest degree involved the milk possesses infectious 

 properties, and is therefore dangerous. Tubercle bacilli have been 

 found in large numbers in the milk and the udder under such cir- 

 cumstances. Unlike other affections of the udder, tuberculosis of 

 this organ does not at once change the appearance and the quality of 

 ' the milk secreted. Bang states that for at least a month after the 

 disease has appeared the milk is normal in appearance and may be 

 consumed and sold without arousing the suspicion of the owner. 

 There is, therefore, considerable danger involved in this disease, and 

 the necessity for the careful inspection of dairy cows seems more 

 urgent than ever before. 



Authorities are, however, not fully agreed as to whether the milk 

 from tuberculous cows in which the udder is apparently not invaded 

 by the disease should be considered dangerous or not. Some are 

 inclined to believe that the milk secreted by healthy udders is never 

 infectious, even when the lungs or other organs are affected; that, 

 in other words, the tubercle bacilli are rarely, if ever, separated from 

 the lesions which they produce, and that the udder itself must be 

 diseased before tubercle bacilli can appear in the milk. Experi- 

 ments made with the milk of tuberculous cows in which there were 

 no indications of udder disease do not bear out this theory, since 

 tubercle bacilli have been found in the milk of such cows. Some 

 authorities still believe that the udder is diseased when the milk is 

 infected, but that the disease escapes observation. However this may 

 be, the fact that the udder may be diseased and the disease not rec- 

 ognizable, simply casts suspicion upon all milk from tuberculous 

 animals. We know that the milk of tuberculous cattle may or may 

 not contain tubercle bacilli when the udder is apparently free from 

 disease. But we have no rapid method of determining whether, in 

 any given case, the milk contains tubercle bacilli or not. Moreover, 

 the bacilli may be absent at one time and present at another in milk 

 from the same cow. When we consider, therefore, the extent of tuber- 

 culosis and the hidden character of the disease, a certain amount of 

 suspicion rests upon all milk. Fortunately tubercle bacilli are readily 

 destroyed by the temperature of boiling water, and hence both meat 

 and milk are made entirely safe, the former by the various processes 

 of cooking, the latter by boiling for a few moments. Until better 

 means of diagnosis are at hand it is incumbent upon all communities 

 to have dairy cows examined or inspected, at least to the extent of 

 finding out whether the udder shows any signs of disease. If this is 

 detected, the affected animal should be killed at once, or else all 

 opportunity for the sale of such milk removed by appropriate meas- 

 ures. The dangers from infected milk might by these means be very 

 materially lessened. 



