DISEASES CAUSED BY INFECTED MILK 103 



corresponds, in that cows kept under unsanitary condi- 

 tions are much more apt to become infected than those 

 that live an outdoor life, with good food, etc. 



The percentage of tuberculosis in cattle varies greatly 

 with the refinements of diagnosis. Thus the percentage of 

 reactors to the tuberculin test would be very much greater 

 than the percentage showing clinical manifestations of the 

 disease. 



The New Jersey Tuberculosis Commission found some- 

 thing like sixteen per cent of the cattle examined to be suf- 

 fering from tuberculosis. In Saxony no less than thirty per 

 cent of all cattle are believed to be infected by this disease. 

 In Copenhagen, Professor Bang has shown the disease to 

 be very prevalent. In Denmark, the percentage is estim- 

 ated at about seventeen per cent. In Leipzig, thirty-three 

 per cent of the cattle over one year old slaughtered in 1895 

 were found to be tuberculous. 



Fifteen to twenty -five per cent of all the cows supplying 

 the District of Columbia have tuberculosis, according to 

 estimates of government officials. Perhaps a similar per- 

 centage applies to the cattle supplying the milk of other 

 large cities. There is much more tuberculosis in some parts 

 of the country than in others. As we go west we find less 

 tuberculosis among the cattle who live a natural life upon 

 the ranges. The disease increases when cattle are impris- 

 oned in stables, with poor air, lack of exercise, exposure to 

 infection, and other unsanitary conditions. For the same 

 reason the most tuberculosis in human beings occurs in 

 crowded quarters and where people live under bad 

 hygienic conditions. 



Tubercle bacilli in milk products. When tubercle bacilli 

 are present in milk they collect in about equal proportions 

 in the cream and sediment. This is equally true when 

 cream separates slowly and naturally (gravity cream), 

 or when it is forced to the surface quickly by the use of 

 a centrifugal machine (separator cream). Tubercle bacilli 



