382 



The Diseases of Animals 



method of infection), or by being taken in with the 

 food or by being inhaled and taken into the lungs. In 

 the transmission of the disease from one animal to 

 another, the germs are probably conveyed by one of the 

 last two methods. Suckling calves may get the germs 

 in the milk from a tuberculous cow, or they may take 

 them upon dry food or in drinking water, where they 



Fig. 56. Section of tuberculous lung. 



were scattered by diseased animals. It is probable that 

 the discharge from the nose, which contains the germs, 

 being dried, is stirred up in the form of dust, and 

 when inhaled by healthy animals produces the disease. 

 In a few cases it is possible that the disease may be con- 

 genital. Such cases are rare, and occur only when the 

 cow's generative organs or her whole system are 

 diseased. 



