294 Specific IiiHaDniiatioiis. 



The contagion is carried from animal to animal in the same way. 

 Cattle and hogs affected with pulmonary tuberculosis discharge 

 bronchial mucus loaded with tubercle bacilli by their coughing ; and 

 this is inhaled as fine spray-like droplets by other animals standing 

 near h\, or falls upon the fodder or into the water and with these 

 substances may gain entrance to a new animal body. One of the 

 most important sources of tuberculous infection both for man and an- 

 imals is the milk of cattle affected by tuberculosis of the udder ; 

 milk from such a source may, as shown by Bangs, remain apparently 

 normal even for weeks though it contain millions of tubercle bacilli. 

 If swallowed in raw state, as used in the feeding of calves and pigs, 

 such milk gives rise to infection of tlie body by way of the alimen- 

 tary canal and chyle vessels, as proved by experimental feeding. 

 The general milk from a dairy may become infected if there be 

 but one cow^ in the stalls with tuberculosis of the udder, provided 

 that cow be milked with the rest and her milk mixed with that 

 from the other cows. 



Again the intestinal discharges of consumptive animals contain 

 the infection, either because these animals, as is often the case, 

 have tuberculous ulcers of the intestine, the bacilli from which be- 

 come mixed with the excrement, or because the animals swallow 

 their pulmonary expectorate and the bacilli pass through the bowel 

 without being all destroyed. The vaginal discharge from cows with 

 uterine tuberculosis furnishes another source of infection. Th'2 

 straw saturated with these infectious discharges, should it happen 

 to be eaten by other cattle with their fodder, may serve as a means 

 of transmission of the disease. Occasionally infection occurs in 

 coition, as the vaginal secretion may be carried from one animal to 

 another by the male, or the latter, when tuberculous, may transmit 

 his own bacilli in the spermatic fluid. Tuberculous infection of 

 cutaneous wounds is rare among animals, although occasionally in 

 man post mortem section of tuberculous organs gives opportunity 

 for this mode of infection. 



The horse is usually infected with tuberculosis by eating straw 

 (soiled with the tuberculous discharges of cattle) ; the dog often 

 by licking up human tuberculous sputum ; the cat by drinking tuber- 

 culous milk. The disease develops in fowls where the latter have 

 opportunities to pick up human sputum or tuberculous discharges 

 from horses, cattle or hogs ; the excrement of chickens already 

 affected with intestinal tuberculosis, however, affords the greatest 

 chance for the infection of the other feathered inhabitants of the 

 premises (soiling of food, ground, etc.). 



