xxvi Report of the Veterinarian. 



hence presumably exposed to the infection for the first time. It is 

 rather the rule than the exception that a cow does not abort a second 

 time, and it is very unusual to have them abort a third year in succes- 

 sion, apart from some especial cause other than infection. 



Although the cow continues to carry the germ for a length of time, 

 she appears to become early immune from its pathogenic action on her 

 own system, and while it is important to rid her of its presence, this is 

 rather as a part of the general disinfection for the protection of other 

 animals that are yet susceptible than as a means of guarding her 

 against a new abortion. 



Very much remains to be done in this field, and, to give entirely 

 satisfactory results, a herd should be maintained under constant control 

 and scientific observation. 



Respectfully, 



James Law. 



