Susceptibility to Tuberculosis. 519 



Chauveau and Arloing have demonstrated that asses may be readily infected by 

 intravenous injection of tubercle bacilli. 



Among dogs and cats tuberculosis is particularly frequent in large cities. 

 Thus Frohuer found 27 tuberculous dogs among 62,-500 patients observed in the 

 ambulatory clinics in Berlin, that is, 0.09%. Johne and Eber in Dresden found 

 11 out of 400 dogs tuberculous and but one among 100 cats. Jensen in Copenhagen 

 found in the course of 2 years 5.7% of tuberculous animals among 28 dogs and 

 25 cats; Petit & Basset in Alfort found, among 2,717 dogs examined, 152 infected 

 T7ith tuberculosis. 



The breed of an animal may influence its susceptibility 

 to tuberculosis. The fact that tuberculosis occurs more fre- 

 quently in some breeds than in others is due in a great measure 

 to the different conditions under which they may be kept or 

 the uses to which they may be put. Cattle from the Russian 

 steppes, for example, become infected just as readily as the 

 more domesticated breeds when they are removed from pasture 

 and fed in stables (working oxen!). On the other hand the 

 young animals of the latter breeds on mountain pastures are 

 much less frequently affected with tuberculosis than animals 

 raised in barns. However that may be, a greater resistance 

 to artificial infection can be demonstrated to exist in the cattle 

 of the steppes and, according to Kitasato, in the Japanese 

 breeds of cattle. The observation that the breeds of the low- 

 lands are more generally affected than the breeds of moun- 

 tainous regions is explained by the fact that the former, on 

 account of their greater milk producing capacity, constitute the 

 large dairy herds and are kept in stables of large estates and 

 of dairies where they are milked as much as possible (Roeckl, 

 Bongert). 



In the municipal abattoir of Budapest, in the years 1899-1902 the percentage 

 of tuberculous cattle among the gray breeds of the plains did not exceed 0.23% 

 and among the cows of the Hungarian breeds, which are also kept out of doors 

 the morbidity was 4.0 to 6.1%. The Hungarian working oxen, on the other hand, 

 that had been kept in stables for several years and at work were tuberculous to 

 the extent of 13.6-18%,, while of the cows of the colored breeds 14.8-17.2%© were 

 tuberculous. According to Kitasato the native Japanese cattle, under normal con- 

 ditions, are free from tuberculosis while imported breeds and cross breeds frequently 

 acquire the disease. The injection of highly virulent tuberculous material into 

 52 native calves and 19 calves from these cross breeds showed that the native 

 cattle withstood the subcutaneous injections without harm and that they could 

 be made seriously ill only by means of intravenous or intraperitoneal injections. 

 Similarly, Hutyra found that calves of the Hungarian long horned breeds were 

 difficult to infect by the inhalation of bovine tubercle bacilli in contrast to the 

 easy infection of the calves of the ordinary colored breeds. 



Individual susceptibility is not the same in all animals of 

 the same susceptible breed. In large herds where the disease 

 has been thoroughly established, certain animals are always 

 found that may be perfectly healthy and live to a considerable 

 age, although they are constantly exposed to the same danger 

 of infection as their mates. In experiments of artificial in- 

 fection also it is noted that among animals of the same breed 

 and age some resist infection with large masses of virulent 

 bacilli. This individual immunity may be congenital, or it may 

 be acquired in the sense that the animals in question may have 



