IMMUNITY 251 



tions and the objects with which they have been in contact, 

 and by the proper disposal of their bodies. A personal 

 knowledge of the nature of the organism and of its method 

 of distribution is tin- only tiling that enables one to protect 

 himself or his herds and Hocks. 



Necessity for correct diagnosis. It is very essential that 

 a correct diagnosis of any of the transmissible diseases be 

 made, for the methods that will prove effective against one 

 may have no effect against another. Especially is this true 

 when serums or vaccines are to be used in preventing fur- 

 ther spread, for these substances are specific in their action. 

 The farmer must usually rely on the experienced veterin- 

 arian for a proper diagnosis of any transmissible disease, 

 and the veterinarian is frequently forced to call to his aid 

 the facilities of a bacteriological laboratory. 



The use of drugs in the treatment of the transmissible 

 diseases is usually without any curative effect. The farmer 

 must exert himself to prevent the disease, and especially to 

 prevent their introduction on his farm. 



