496 THE TUBERCLE BACILLUS GROUP 
Bovine infections in man are much more common in children than 
in adults.^ Wang^ has studied the distribution of bovine bacilH in man 
by the method of sputum examination. Of 998 cases examined, 3 
cultivations contained both human and bovine bacilli, and 4 contained 
bovine tubercle bacilli alone. Milk is a frequent vehicle for the trans- 
mission of the virus to man; the origin of the bacilli in milk has been 
summarized by Moore^ as follows : 
"1. Cows with tuberculous udders eliminate tubercle bacilli with 
the milk. In such cases these organisms are usually present in large 
numbers, 
"2. Cows with glandular or pulmonary tuberculosis, in which the 
lesions are discharging into the bronchi, eliminate tubercle bacilli with 
the feces and with the droolings. In cases of intestinal tuberculous 
ulcers the organisms are excreted with the feces. 
"3. Milk is usually infected with tubercle bacilli when it is taken 
from cows with tuberculous udders. It may, through contamination 
with feces or uterine discharges, be infected when drawn from cows 
with open lesions in the respiratory and digestive tracts or organs of 
reproduction. 
"4. Tubercle bacilli are not, as a rule, present in milk of cows that 
react to tuberculin and which, on careful physical examination, exhibit 
no evidence of disease." 
The identification of tubercle bacilli in milk presents no insurmount- 
able difficulties, but certain precautions must be observed. Prudden 
and Hodenpyl,^ Straus and Gamaleia^ and others have shown that the 
injection of killed tubercle bacilli into guinea-pigs by the intraperi- 
toneal route will induce tubercle formation even if the organisms have 
been heated in the autoclave. These tubercles, however, if crushed 
and injected into fresh animals, do not reproduce tubercles. It is 
obvious that the injection of pasteurized milk containing dead tubercle 
bacilli may lead to false conclusions unless this possibility be borne in 
mind. The bacillus of infectious abortion induces lesions in guinea- 
pigs closely simulating tuberculosis.*' This organism is rather widely 
distributed in unheated milk.^ 
Method.— Ten to 20 cc. of milk are centrifuged for one-half hour 
and from 5 to 10 cc. of the sediment and lower portion of the sample 
are injected subcutaneously into guinea-pigs. The cream layer is 
also injected subcutaneously into a second pig. After three to six 
weeks, if the animal shows signs of emaciation, 0.5 cm. of undiluted 
bovine tuberculin is injected. This injection usually results fatally. 
In any event the animal is killed and the bovine tubercle bacilli are 
identified in the usual manner, 
^ Statistics by Park and Krumwiede, p. 47('). 
2 Lancet, 1916, ii, 417. ^ Jour. Med. Res., 1911, 24, 517. 
* New York Med. Jour., 1891, 53, 637, 697. =■ Arch. med. Exper., 1891, 3, 705. 
« Theobald Smith: Bureau of Animal Industry, 1894, Bull. 7, p. 80. Smith and 
Fabyan: Centralbl. f. Bakteriol., orig., 1912, 61, 549. 
' Melvin: Vet. Jour., 1912, 68, 528. Fabyan: Jour. Med. Res., 1913, 28, 85. 
