270 



INFECTIOUS DISEASES 



they were purchased, or became infected through exposure to the 

 disease in the public stock-yards and stock-cars. The shipping 

 of feeding hogs from one section of the country to another, and 

 from public stock-yards, has always been productive of hog- 

 cholera. Dr. Dorset states that more than fifty-seven per cent 

 of the hog-cholera outbreaks are caused by visiting, exchanging 



Fig. 



'0. — A hug yard wht-ru tin; diacasc-pruduciug germs may bu carried over from year 



to year. 



work, exposure on adjoining farms and harboring the infection 

 from year to year (Fig. 79), and more than twenty-three per 

 cent to purchasing hogs and shipping in infected cars, birds and 

 contaminated streams. 



In neighborhoods where outbreaks of hog-cholera occur neces- 

 sary precautions against the spread of the disease are not taken. 



