TUBERCULOSIS IN ANIMALS 327 



tuberculosis or affected with its latent form which may lead to recovery, 

 or to a more actue, eventually fatal outbreak. The most careful 

 postmortem examinations on human material show that probably 

 not less than 70 to 90 per cent, of all persons, no matter from what 

 disease they may die, have at some time had a tubercular infection. 

 Pulmonary tuberculosis has often been found absent among uncivil- 

 ized tribes living in a state of nature, but contact with civilized races 

 soon causes it to appear among them and often to become frightfully 

 prevalent, as among the Indians and negroes in the United States. 

 Another good example of the same tendency is found among the 

 inhabitants of the Philippine Islands, who before the advent of the 

 Spaniards were apparently free from tuberculosis. Now, tuberculosis 

 is frightfully prevalent among those tribes which have come into 

 contact with the civilized races for several hundred years. One- 

 encouraging feature in regard to the prevalence of tuberculosis lies 

 in the fact that the mortality and evidently also the number of persons 

 affected has diminished since its cause and manner of spreading has 

 become known and made precautions and prophylaxis possible. In- 

 Germany the death rate per year per 1000 inhabitants has fallen 

 from 3.1 to 1.9 from 1890 to 1903; and in the United States from 

 1890 to 1900, from 2.544 to 1.095 per year per 1000 inhabitants. 



Tuberculosis in Animals. Tuberculosis among animals, in the wild 

 state, both mammalians and birds, is practically unknown; but it is 

 quite prevalent among domestic animals and among wild animals 

 confined in zoological gardens, menageries, etc. Monkeys, which 

 in nature are never found to be infected with tuberculosis, generally 

 die from it in captivity; guinea-pigs and rabbits, which are the most 

 susceptible common laboratory animals, and very frequently used 

 in inoculation experiments, are rarely affected spontaneously even 

 in captivity. Antelopes, giraffes, zebras, wild animals of the canine 

 and feline tribes, often contract the disease in confinement. Wild 

 birds in aviaries often contract the avian type of the disease, but 

 with the exception of parrots, rarely the mammalian type. 



Tuberculosis has also been observed in goats, sheep, dogs and cats 

 and quite frequently among domestic fowl. 



Cattle. Tuberculosis among cattle running wild on extensive steppes 

 and prairies is rare, but when the animals are kept in barns, crowded 

 and subjected to stable feeding, it becomes very common. It reaches 

 its highest percentage among milch cows, which are often kept under 

 the most unnatural and unhygienic conditions. There are cases 

 on record where more than one-half and up to 80 per cent, of a herd 

 of milch cows have been found infected. 



Hogs. The disease has become widespread among hogs since it 

 has become customary to feed them on skimmed milk which has 

 been returned from the creamery. The milk from a few cows affected 

 with obvious or latent tuberculosis, when mixed with a large amount 

 of milk from unobjectionable sources, may infect the entire quantity, 



