MILK-BORNE INFECTIONS 461 



before they were many generations old. As a matter of fact, 

 after a number of generations the culture characteristics of the 

 two strains approach each other and differentiation becomes more 

 difficult. On the other hand, human beings have been infected 

 with bovine tubercle bacilli in slaughter houses, and later pul- 

 monary tuberculosis and tuberculosis of internal organs have 

 developed. It is possible that the original infection with bovine 

 tubercle bacilli was superimposed upon infection from human 

 sources. In all these cases transformation of the two types of 

 tubercle bacilli is not a necessary conclusion. 



It is clear that the bovine type of tubercle bacilli is distinct 

 from the human type, and that the human type is more virulent 

 for man than the bovine type. In adults tuberculosis caused by 

 bovine bacilli is rare and might perhaps be called negligible, if 

 it could be safely assumed that Von Behring's theory of infection 

 in childhood is incorrect. In children bovine infections constitute 

 about one-fourth of all cases of tuberculosis, and 6J to 10 per cent, 

 of the total fatalities from tuberculosis among children are due 

 to bovine infections. This is surely not a negligible quantity. 

 The necessity of freeing milk-supplies from living tubercle bacilli 

 is obvious. This problem must be attacked, and has been at- 

 tacked with some success by two procedures: 1, Through eradica- 

 tion of tuberculosis among milk cows, and, since this requires 

 much time for successful completion, 2, by pasteurization of all 

 milk. 



The following figures given by Kiernan show what has been 

 accomplished toward the eradication of tuberculosis among cattle 

 in the District of Cloumbia during the years 1910 to 1917: 



THE ERADICATION OF TUBERCULOSIS IN THE DISTRICT OF COLUMBIA BY THE USE OF 

 THE TUBERCULIN TEST 



Total 11,542 Average. . . . 4.08 



Foot-and-mouth Disease. This disease is widely dissem- 

 inated in European countries, and quite a number of sudden 

 epidemics have been experienced in this country. The cause of 

 this disease is an ultramicroscopic organism. It is an affection 

 of the mucous membrane of the mouth and of the skin between 

 the toes and above the hoofs. Vesicles form and later rupture. 

 Sometimes the udder is affected. The milk from diseased cows 



