324 VETERINARY BACTERIOLOGY 



in coughing and the contamination of drinking- vessels are common 

 sources of infection. Material coughed up from the lungs by 

 cattle is commonly swallowed, and both pulmonary and intestinal 

 tuberculosis in these animals results in large numbers of organ- 

 isms being thrown off with the feces. This is probably the most 

 important channel of exit in the cow. Tuberculosis in swine fol- 

 lowing cattle is undoubtedly due to the ingestion of bacteria voided 

 in this manner. Contamination of milk with tubercle bacilli is 

 almost inevitable when they are constantly present in the feces. 

 Milk is also found to contain tubercle bacilli when lesions are 

 present in the udder. Whether or not they may be present when 

 the udder is not tuberculous is a mooted question, but as the 

 bacilli can rarely if ever be demonstrated in the blood, it is not 

 probable that they can enter the milk direct when 'the udder lesions 

 are absent. The urine may occasionally contain the bacteria. 



The disease is probably never inherited, the offspring being in- 

 fected only when the disease infects the uterus and the placenta. 

 This fact is of importance, for upon it the Danish veterinarian, 

 Bang, has outlined a practicable method of building up herds free 

 from tuberculosis. The calves are separated from their tuberculous 

 mothers soon after birth and are fed only upon pasteurized milk. 

 Those animals known to be tuberculous are separated from the 

 others and a quarantine strict enough to prevent the transfer of 

 the disease from infected to non-infected animals is established. 



Infection Atria in Tuberculosis. The portals of entry of 

 Bacillus tuberculosis have been investigated at length in recent 

 years, but there are still discrepancies in the results of investigators 

 that are unexplained. One group of tuberculous infections, par- 

 ticularly the pulmonary type in man, is probably due to inhalation 

 of the organisms. This was at one time universally conceded, but 

 the work of Calmette and others has shown that primary pul- 

 monary tuberculosis may result from ingestion of the organisms. 

 Certain investigators believe this to be far more common than in- 

 fection by inhalation. It has been shown that the tubercle bacilli 

 may be demonstrated in the thoracic duct of a dog fed upon the 

 organisms within a few hours after their ingestion, and without 

 any apparent lesion of the intestinal wall. The alimentary tract 

 is undoubtedly the infection atrium in most cases of intestinal 



