90 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
the disease. Findel, Reichenbach and Alexander’? found 
that at least 400,000,000 tubercle bacilli are necessary 
to produce infection when only a single dose is fed to 
guinea pigs and that 800,000 tubercle bacilli given fifty 
times by the mouth are not certain to produce infection. 
Ostermann *® reports that milk containing 1000 bacilli 
per cc. may be repeatedly ingested without effect. 
Fliigge and his co-workers also found that while a very 
few tubercle bacilli are sufficient to produce a severe 
tuberculosis when injected into a guinea pig, 200 are 
necessary when the bacilli are inhaled and 140,000,000 
when they are ingested. 
4. How can Contamination of Market Milk with 
Tubercle Bacilli be Prevented?—The information at 
hand shows that cows with tuberculosis of the udder are 
by far the greatest factors in infecting market milk with 
tubercle bacilli and that next in order are those with ap- 
parently healthy udders but showing clinical symptoms 
of the disease in other organs. Compared with these 
two classes, cows which present no evidence of tubercu- 
losis except a reaction to the tuberculin test are a rather 
insignificant source of contamination. 
The contamination of milk with tubercle bacilli can 
be most thoroughly and most certainly prevented by re- 
moving from the herds concerned in a milk supply the 
cows belonging to all three classes. This could only be 
accomplished by making a tuberculin test and physical 
examination and repeating them at certain intervals. A 
19 Cited by Ostertag, Zeitschr. fiir Fleisch u. Milchhy., p. 
27, No. 2, vol. xxiii. 
20 Cited by Klimmer, Osterreich. Wochenschr. fiir tierheilk. 
4. Tierzucht, No. 45, 1912. 
