34 CITY MILK SUPPLY 



Infection of Milk by Germs of Tuberculosis in the Feces. That 

 milk might be infected with tuberculosis by contamination with the man- 

 ure of cows afflicted with the disease, was pointed out by Sedgwick and 

 Batchelder in 1892 in their paper on the bacteriological examination of 

 the Boston milk supply but the gravity of the menace was not appre- 

 ciated till Shroeder and Mohler in 1906 emphasized its importance. 



Efforts have been made at Washington, at the Cornell, Minnesota, 

 Nebraska and Illinois Agricultural Experiment Stations and by the 

 English Royal commission to determine the frequency with which tuber- 

 cular cows pass the germs of the disease in their f eces. In the six instances 

 147 animals were studied and 16 of them were proven to be passing the 

 bacilli. Eleven of these reactors were slaughtered and every one was 

 badly tubercular; they all had abscesses of the lungs, seven had ulcers 

 of the intestines and six tuberculosis of the liver. Of the five animals 

 not autopsied one was manifestly tubercular and the others were not. 

 From this series of experiments it seems evident that animals in ad- 

 vanced stages of tuberculosis pass tubercle bacilli in their feces and that 

 animals seemingly in good health may do so. 



Frequency of the Infection of Milk with Tuberculosis. The milk of 

 tuberculous cows is likely to contain the germs of the disease and so unless 

 heated to a high enough temperature to kill them is a potent factor in 

 spreading the disease, not only among the calves and swine that may be 

 reared on it but to man himself. In discussing the frequency with 

 which milk carries tuberculosis germs, there are to be considered: (1) 

 milk from cows having tuberculosis of the udder; (2) milk of tuberculous 

 cows without such a lesion; and (3) market milk. 



There is no question at all as to whether cows with tuberculous 

 udders yield milk that carries the germs. Authorities are agreed that 

 in all but very rare cases such milk contains enormous numbers of the 

 germs in a highly virulent condition. A cow with a tuberculous udder 

 is such an ugly menace that she should be sent to the shambles at once. 



As to whether the milk of tuberculous cows whose udders are un- 

 affected is infectious or not there is considerable difference of opinion. 

 Briscoe and MacNeal record tests of the milk of 748 tuberculous cows 

 without recognizable disease of the udder, and of the samples tested in 

 various ways 13 1 proved positive. However, many of the positive 

 results were secured by early investigators who doubtless did not take 

 elaborate precautions to prevent the milk becoming infected from external 

 sources. In the later important work Ostertag at Berlin in 1899 exam- 

 ined the milk of 50 cows finding the milk of 49 negative and one doubtful 

 and in 1901 that of 18 cows was all negative. Miiller in Germany, in 

 1899 tested the milk of nine cows finding it all free from the germs and 

 Smit at Rotterdam in 1909 likewise got negative results from the milk 

 of 35 cows. On the other hand, DeJong at Leiden in 1908 found that 



