^44 Veterinary Medicine. 



epizootic. While the tuberculosis of barnyard fowl is a manifest 

 variety and not readily interchangeable with the varieties affect- 

 ing the mammal, yet, with a special predisposition, it can be 

 transferred and can then be conveyed from animal to animal in 

 the new genus in which it has been implanted. That of cage 

 birds is interchangeable with that of man. 



Rodents. Guinea-pigs have a strong susceptibility to tubercu- 

 losis, whether from human or bovine source, and rabbits for that 

 of birds, and by continuous transmission through the body of the 

 rodent, all alike seem to tend tqjvard acquiring common charac- 

 ters. The Guinea-pig, therefore, has been especially availed of 

 for the experimental transmission of tuberculosis, and, as the dis- 

 ease in them becomes acute and rapid in its progress, these sub- 

 jects permit the multiplying of experiments in a short period. 

 Rabbits are less vulnerable to the bovine or human form. 



Sheep and goats, kept under usual conditions, show a re- 

 markable immunity from tuberculosis, yet if directly inoculated 

 an inherent susceptibility is easily shown. Habitual immunity 

 may be in some degree due to their open air life, to the heavy 

 winter fleece protecting them against chills, to the comparative 

 absence of the heavy and continuous milk yield demanded of 

 cows, to the more restricted development of the lymph plexuses 

 in the lungs and elsewhere, and to the limited opportunity offered 

 by the small tonsils for infection entrance. 



The horse, ass and mule rarely contract tuberculosis casually, 

 the more spacious stall, outdoor life, hard muscular condition, the 

 very small tonsils, the exclusive nasal respiration, the paucity of 

 connective tissue lymph plexuses, and the abundance of red 

 globules, probably favor immunity. Yet on inoculation by 

 Chauveau, Nocard and others, the horse readily succumbed to 

 infection, generalization taking place more certainly than in the ox. 



Cattle. The bovine races are remarkably subject to tubercu- 

 losis. This is probably due in part to the great amount of con- 

 nective tissue lymph plexus in the lungs and elsewhere, the habit 

 of using the mouth in hurried breathing, the deep, sudden in- 

 spiration through the mouth and over the tonsils that follows a 

 cough, the habitual restricted size of the cow stables, the absence 

 of individual separated stalls, the habit of feeding from the same 

 trough with the cattle adjacent, the great drain of yearly breeding 



