TUBERCULOSIS 313 



and, when the disease occurs, it most probably originates 

 by contact with civilisation. Two familiar instances are the 

 Chartley wild white cattle, and wild rabbits at times when 

 they get excessively numerous, especially during certain seasons 

 when they confine themselves much to their burrows. Once 

 introduced, the close atmosphere of the burrow favours its 

 dissemination. Open air, sunlight, and free ventilation are 

 the best safeguards of stock, as of the human species. 

 Excluding animals that are kept out of doors, and calves, 

 about 30 per cent, of all cattle slaughtered in this country are 

 reported to be tuberculous. The disease is rare in animals 

 under one year old, and it is very exceptional to find it in 

 calves under a month old. Of cattle kept on the open camp 

 in Argentina, only about one per thousand suffers from a 

 taint of tuberculosis. In town dairies where cows are crowded 

 together in dark ill-ventilated buildings and simultaneously 

 milked and fed for the butcher, within twelve months 50 

 per cent, are not infrequently affected. Professor Nocard, 

 the great French authority, who has done much to advance 

 our knowledge of the disease, says that in his experience 

 "15 to 25 per cent, of cows in the country are tuberculous,- 

 but that not one calf in ten thousand is diseased." The milk 

 of an affected cow is not perceptibly decreased in quantity, but 

 it is lowered in quality. The responsible bacillus thrives best 

 in darkness, at temperatures from 80 to 105 F. Affected 

 cattle showing no external signs of disease may be a source of 

 infection to others with which they come in contact. The 

 seats of disease in cattle are the various lymphatic glands of 

 the body (early centres of infection are the glands close to the 

 bifurcation of the bronchial tubes), the lung, the intestine, and 

 the udder. Next to the glands in the chest cavity, the lung 

 is by far the commonest seat of the disease, besides being the 

 most likely to act as a means for communicating it. Next in 

 order comes the intestine, and finally the udder. About 3 per 

 cent, of tuberculous cattle have a lesion in the udder, and it is 

 only when a lesion discharges into the flow of milk that 

 danger from it may be anticipated. The bacillus may even 

 then be removed by the use of the centrifugal cream separator, 

 in the slime of which the organisms accumulate. 



Animals with pulmonary tuberculosis have a persistent 

 cough. The temperature is slightly raised, and they become 



