518 Tuberculosis. 



Infection from cutaneous lesions is exceedingly rare and 

 in such cases the disease usually remains localized or spreads 

 at most to the adjacent lymph glands (Lydtin, Johne). Much 

 greater danger as far as the source of infection is concerned 

 is presented by castration wounds, which are rather rare in 

 cattle (Bongert) but more frequent in swine as a result of the 

 application of milk or the infection of the litter Avith excre- 

 tions. Sometimes infection may follow the application of 

 sputum to the wound by a consumptive operator (Tempel, Jahn, 

 Michael). 



The mode of infection varies to a certain extent according 

 to the species of animal. Cattle, it seems, are always infected 

 by the products of diseased animals of the same species. Thus 

 calves are usually infected by means of infected milk while 

 older animals are infected by the ingestion of solid food or 

 of contaminated drinking water or by the inhalation of infected 

 air. In horses tuberculosis usually begins in the alimentary 

 canal ; occasionally this is produced by infected material derived 

 from tuberculous fowls (Nocard), but in most cases by infec- 

 tious material of human origin (Eobert, Roder). — In pigs tuber- 

 culosis occurs in a vast majority of cases as a result of feeding 

 cows' milk or whey. Feces of diseased cattle are next in im- 

 portance as a source of tuberculosis in swine, infection with 

 this material usually occurring by way of the pharynx or the 

 intestinal tract ; a pig with diseased teats may infect its young 

 while suckling; and finally the inhalation of tubercle bacilli is 

 probably also an occasional cause. — Sheep and goats are prob- 

 ably always infected by diseased cattle. — The infection of dogs 

 and cats usually stands in causal relation with tuberculosis in 

 man. As a rule pet dogs become infected by licking the sputum 

 of their consumptive owners or by inhaling infected air, while 

 cats have become infected by the ingestion of infected milk. 

 (The tuberculous dogs examined by Petit came, for the greater 

 part, from poorly kept saloons and coffee houses which were 

 much frequented by laborers.) 



Susceptibility to tuberculosis varies according to the species 

 of animal. Among domestic animals cattle and swine are most 

 susceptible to artificial infection while other animals possess 

 much more resistance. The natural resistance of any species of 

 animal may be overcome by intensive and repeated infection. 

 In reality, however, buffalo, horses, sheep, goats, dogs and cats 

 acquire tuberculosis only rarely in spite of their frequent ex- 

 posure to diseased cattle or human beings. 



The frequency of tuberculosis among the different species of domestic animals 

 is shown in statistical tables furnished by slaughter house reports (see page 502). 

 — Among buffalo the disease appears to be less common in Russia than it is in Hungary, 

 where, at the abattoir of Budapest, it is sometimes found in 0.9% of all slaup'htered 

 animalp. Kanzelmacher found only 5 head infected among 2,715 buffalo slaughtered 

 at Tiflis, i. e., 0.02%. — Among asses Blanc, Pleindoux and Nocard each observed 

 one case of tuberculosis. The fact that this disease seems to be so rare in this 

 species may be due to the small number of observations, at least. Stockmann, 



