CHAPTER XXVIII. 



CONTAGIOUS BIS'EASES— continued, 

 TUBERCULOSIS. 



Definition. — An infectious, infective, and inoculable disease 

 induced by the action, particularly upon the hereditarily pre- 

 disposed, of a bacillus discovered by Koch in 1882, and termed 

 the Bacillus tuberculosis, affecting many kinds of animals, and 

 in consequence called by Lydttiu the "universal panzootic." 



Tuberculosis is most commonly seen in man, monkeys, and 

 horned cattle, less frequently in the pig, horse, dog, and cat, and 

 birds ; amongst the latter, however, it sometimes assumes an 

 epizootic form, attacking poultry, pigeons, pea and guinea 

 fowls, turkeys ; even small birds not being proof against its 

 ravages. The smaller ruminants, sheep and goat, are very 

 rarely attacked with tuberculosis ; they may resist subcutaneous 

 inoculation, but they are not proof against its intravenous inocu- 

 lation. The direct introduction of the bacilli into the blood, 

 and the repeated ingestion of tuberculous growths, induces the 

 disease even in them. It is also found in the camel, giraffe, 

 antelope, llama, gazelle, zebra, &c., and it is now well known 

 that the disease is transmissible from man to animals, and from 

 animals to man. 



The tubercular nodules vary in appearance, some being grey, 

 like pearls, hence the term " pearl disease " in England, " perl- 

 sucht " in Germany ; some being yellow, and some calcareous, 

 these varying appearances indicating the age of the growths. 

 They are non-vascular, and vary much in size, some being even 

 smaller than a millet seed (miliary tubercle), very numerous, 

 and invading one or many organs. Some larger ones are hard, 

 greyish-red, pedunculated, or having broad bases, arranged in 

 clusters of various sizes, covering the lungs, thoracic walls, surface 

 of diaphragm, the peritoneum, &c. ; or they are found in the form 

 of great fluctuating masses tilled with yellow pus, which is thick, 

 grumous, full of calcareous grains, resembling mortar, or of an 



