DISEASES OF CATTLE 241 



Dr. Robert Koch, a distinguished German physician, who discovered 

 the germ of the disease in the year 1882, and named it Bacillus tuber- 

 culosis. He proved by experiment that the disease is produced by 

 these germs and without them the disease can not be produced. It is 

 now universally admitted that tuberculosis is a contagious disease 

 and may be transmitted from animal to man. 



In America the disease was introduced with early importations 

 of cattle and has been with us ever since. Modern methods of trans- 

 portation by rail and water have spread the disease from one end of 

 the continent to the other. No part of the country is entirely free 

 from it, but it is more prevalent near the great centers of population 

 than in the remoter parts. 



Importance. The importance of the disease must be estimated 

 from two points of view, first, the loss it entails upon the cattle owner, 

 and second, the danger of communication to human beings. 



Consider first its effect upon the pocket of the owner of cattle^ 

 whether farmer, breeder, or dairyman. A serious percentage of the 

 dairy cows of the continent are affected, and the disease is found in 

 even a larger percentage of dairy herds. The disease is commoner in 

 some regions than in others. 



It is no uncommon thing to find as many as 70 or 80 per cent of 

 the cows in a herd diseased. These animals will be in various stages 

 of the disease, some recently infected showing no sign of ill health, 

 others badly diseased, but outwardly appearing healthy, while a few 

 are evidently breaking down and wasting away. 



The loss to the owner is evident when a cow dies of the disease, or 

 when an apparently healthy cow is slaughtered for beef and found 

 so badly affected as to be unfit for food. The calves in such a herd do 

 not long remain healthy. They catch the disease before they are 

 many months old and are a source of loss instead of gain. 



Although the disease is most frequently found in herds that are 

 more or less closely confined, such as dairy herds and purebred cattle, 

 other herds are by no means free from it. Even range cattle are 

 sometimes affected, and the infection spreads in spite of the open-air 

 life of the cattle. 



Tuberculosis is common among hogs. The public abattoirs re- 

 port that a serious percentage of all hogs inspected is found to be 

 tuberculous. The aggregate of these losses among cattle and hogs is 

 enormous, amounting to millions of dollars every year, besides ma- 

 terially decreasing the food supply of the country. 



Turning to the other aspect of the case, the danger of infection 

 of human beings with tuberculosis from cattle, we have only to con- 

 sider a few facts to realize its vital importance to every community. 



Milk is the staple food of infants and young children and is usu- 

 ally taken in the raw state. If this milk is from a tuberculous cow, 

 it may contain millions of living tubercle germs. Young children 

 fed on such milk often contract the disease, and it is a frequent cause 

 of death among them. 



Meat from tuberculous cattle is not so likely to convey the infec- 

 tion, for several reasons. It does not so frequently contain the germs, 



