466 Veterinary Medicine. 



tuberculosis had not time to develop. This mitigating influence 

 held good so long as the deadly plagues were not placed under 

 effective control. When, hovsrever, a nation successfully extir- 

 pated and excluded lung plague and rinderpest, the way was 

 opened for a freer extension of tardily developing plagues like 

 tuberculosis. The great development of beet sugar factories and 

 the accumulation of herds to consume the marc ; the extraordi- 

 nary extension of manufactures which have made England and 

 certain countries of Western Europe consuming rather than agri- 

 cultural lands, and the wonderful modern expansion of dairy 

 husbandry have combined to encrease and concentrate the cattle 

 industry in ratio with the manufacturing and commercial progress 

 of the nations, and as the live stock are kept under a milk-stimu- 

 lating regimen and a life passed largely indoors, the way has 

 been open for an ever-advancing encrease of tuberculosis. In the 

 United States the centralization of population in the Eastern 

 States and in all great centres of industry and the concentration 

 of cows for the milk supply, and in certain districts in connection 

 with butter and cheese factories, have contributed to wide local 

 extensions of consumption. Hence it has been no uncommon 

 thing to find herds in the vicinity of cities with 20 to 100 per 

 cent, affected, in striking contrast with the 0.02 per cent, found 

 in the fat cattle from the plains. 



The modern railway traffic brings to all these swarming centres 

 of animal industry, live cattle from long distances to supply the 

 constant depletion through deaths and the disposal of dry cows, 

 and thus the whole Atlantic slope is drawn upon to fill the east- 

 ern stalls. Infected animals thus shipped from Ohio, Indiana, 

 Illinois, Wisconsin and Michigan for the good of the herds in 

 those states find new homes in New York, or New England, 

 where they have four to twelve months to propagate the infection 

 before they are themselves disposed of. As in the days of the 

 lung plague in America, the eastward trend of bovine traffic, 

 becomes to a certain extent a protection and benefit to the herds 

 of the west, but in equal ratio it operates to the detriment of our 

 eastern stock. What is true of the planting of new centres of 

 infection in the busy dairy districts of the east, and of the steady 

 increase of disease in already infected herds, through the con- 

 stant addition of new cases purchased, is no less true of the cor- 



