82 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



diluted one billion times (Ostertag). 12 In the initial 

 stages, when the tuberculous areas in the udder are small 

 and isolated, the tubercle bacilli are less numerous, num- 

 bering about 1000 per c.c. While such milk must be 

 diluted about 1000 times to render it non- virulent when 

 injected into guinea pigs, it may be repeatedly fed to 

 them undiluted without producing tuberculosis. 



As to the frequency of tuberculosis of the udder, in 

 the post-mortem examination of 1200 cattle reacting to 

 the tuberculin test, nearly all of which were dairy cows, 

 Pearson found the udder tuberculous in 104, or 5.75 per 

 cent. Ostertag estimates that the disease is present in 

 the udder of 0.1 to 0.3 per cent, of all cows. In consider- 

 ing the frequency of tuberculosis of the udder, the large 

 number of bacilli present in the milk in advanced cases 

 must be remembered. The milk of one cow affected with 

 advanced or extensive tuberculosis of the udder can infect 

 thousands of quarts of milk from other cows, if mixed 

 with it, and may even render the entire supply of a 

 small town infectious. 



(b) Cows with Apparently Normal Udders but 

 Showing Clinical Symptoms in Other Organs or Parts. 

 Milk from cows in this condition frequently contains 

 tubercle bacilli. It appears very probable that the udder 

 is actually diseased when tubercle bacilli are eliminated 

 in the milk of such cows. The udder may be tuberculous 

 and yet be apparently normal. The disease is always 

 extensive when clinical symptoms are present, and 

 usually it is generalized tubercle bacilli have repeatedly 

 invaded the blood stream and have had abundant oppor- 



12 Zeitschr fur Fleisch u. Milchhy., pp. 26 and 27, No. 2, 

 vol. xxiii. 



