516 Tuberculosis. 



in one instance 90% of all slaughtered swine were found tuterculous. In Hungary 

 the disease is becoming alarmingly prevalent with the increasing practice of feeding 

 skim milk. 



In an experiment conducted by the Bureau of Animal Industry at Washington, 

 87% of a number of swine that were fed for 3 days with tuberculous milk became 

 tuberculous within 3 to 4 months. When tuberculous milk was fed for 30 days 

 all animals in the experiment became infected with general tuberculosis within 

 50 days thereafter. 



The danger in feeding milk containing bacilli to calves is shown 

 by the common experience that tuberculosis occurs much less frequently 

 in calves that are fed with sterilized milk than in calves that are per- 

 mitted to suckle their infected dams. 



Finally tuberculosis occurs more frequently also in horses in those 

 countries where milk is used in the treatment of sick horses (MacPad- 

 yean. in England), or for food (Bang in Denmark). 



Other food stuffs also and drinking water may act as the 

 carriers of the contagion when they are infected with the secre- 

 tions and excretions of tuberculous animals. Abundant oppor- 

 tunity for such infection is offered in all infected herds. 



The feeding of tuberculous organs from slaughtered ani- 

 mals and the sputum of tuberculous persons are effective means 

 of transmitting the disease to carnivora and omnivora. 



Infection by means of inhalation occurs most frequently 

 in stables occupied by animals affected with pulmonary tuber- 

 culosis. Slowly expired air from infected animals probably 

 contains no infection ( Cadeac & Malet, Cornet) . However, when 

 such air is expelled by coughing the minute particles of water 

 which are expelled with it may contain tubercle bacilli and, 

 similarly, particles of sputum that are thus forcibly expelled 

 will soil and infect the surroundings of diseased animals ( Johne, 

 Bang, Frankel, Fliigge). Thus healthy animals standing in 

 stalls adjacent to those infected with pulmonary tuberculosis 

 are continually breathing infected air while the danger to other 

 animals in the same stables but farther removed from the in- 

 fected ones, is much less. As a matter of fact it is frequently 

 observed that, following the introduction of a diseased animal 

 into a healthy herd, the animals in the immediately adjacent 

 stalls are always the first to become infected. 



Johne was the first to call attention to the importance of the small 

 solid or liquid particles which are expelled in the act of coughing. More 

 recently Fliigge and his pupils have shown that tubercle bacilli which 

 are expelled in the act of coughing, sneezing or even in the act of loud 

 conversation, will infect guinea pigs when properly exposed (spray 

 infection). The same results were obtained by Ravenel by exposing 

 guinea pigs to consumptive cattle in the act of coughing. The results of 

 numerous experiments made with sprays of pure cultures to produce 

 infection by inhalation conform with the former in demonstrating the 

 danger of the moist air of expiration. (See Pathogenesis.) On the other 

 hand the danger of dust infection (Cornet) or of air containing merely 

 dry particles of secretions is considerably less. Experiments with such 

 material gave negative results. Thus Cadeac obtained only 5 positive 



