126 MILK AND THE PUBLIC HEALTH chap. 



42, Norway 8"4, and Belgium 60. In Massachusetts, U.S.A., 

 during 1897, 5 8 '9 per cent of the cases reacted. In Ger- 

 many the figures varied greatly with the locality. Of 48,172 

 cows slaughtered in Saxony during 1899, over 35 per cent 

 were tuberculous. The older the animal the higher the per- 

 centage. Thus, of 14,684 cows over four years old slaughtered 

 in Berlin, 14,556, or 99 per cent, were tuberculous. The 

 lesions, of course, were in some cases trifling, only the bronchial 

 glands being affected. These last figures were, however, founded 

 upon macroscopic examination in slaughter-houses. With the 

 tuberculin test the proportion would be even higher. 



Delepine-' in 1897-99 tested 128 cows with tuberculin. 

 Of these, 37 (30 per cent) were tuberculous. In the testings 

 carried out at Aberdeen in 1899, out of 137 cows tested, 37 

 were tuberculous. 



The tuberculin test has not been used very extensively in 

 this country, but it is probably safe to assume that 25 to 30 

 per cent of cows in this country are suffering from tuberculosis. 



Apart from local incidence of the disease, one important 

 factor influencing the amount of tuberculosis is the age of the 

 cow. Older cows are much more likely to show evidence of 

 tuberculosis. Bang,^ for instance, records that during the 

 years 1898-1904 careful examination of 40,624 head of 

 cattle in Denmark, subjected to the tuberculin test for the 

 first time, showed that of calves under six months 12'1 per 

 cent reacted; of yearlings (from six to eighteen months) 2 7 '5 

 per cent; of two-year-olds (from 1|- to 2|- years) 38-6 per 

 cent ; of full-grown animals (from 2^ to 5) 44'9 per cent ; 

 and of animals over five years 48 per cent — figures which 

 correspond with the results of tuberculin tests in other countries 

 as well as with the experiences of slaughter-houses. 



When the infection was introduced through milk, as 

 when calves were fed upon tuberculous skim milk. Bang noted 

 that while the cows were often very healthy, it was the calves 

 or the young cattle which reacted ; sometimes the peculiar 

 fact might be observed that only animals of the same age — 

 for instance, yearlings or two-year-olds — reacted ; and when 



1 Report of Medical Officer, Local Government Board, 1908-9, p. 402. 

 " Transactions Internat. Congress on Tuherculosis, 1908, vol. iv. part ii. 

 p. 850. 



