COMMUNICATION OF KPIZOOTICS. 15 



In the present state of science we are compelled to 

 admit that the causes of epidemic affections are as 

 little understood as they were centuries since ; and 

 although a strict attention to diet, and protection 

 from the vicissitudes of weather, will go far to render 

 animals insusceptible to diseases in general, it must, 

 nevertheless, be admitted, that these means, valuable as 

 they are, do not give absolute immunity from such 

 attacks. 



Whatever the combination of causes may be which 

 produces these maladies, certain it is that very many of 

 them assume an infectious nature, otherwise we could 

 not account for animals separated and kept apart from 

 those which are diseased, frequently and sometimes 

 altogether escaping, while those are sure to become 

 early victims that are allowed to pasture or live with 

 the affected ; besides, we can often succeed in pro- 

 ducing the malady by inoculating healthy cattle, 

 thus shewing how closely the spread of the disorder 

 depends upon contagion or infection. The fact, how- 

 ever, of animals when in health, if placed with affected 

 ones, contracting a disease of the same kind as that 

 which the latter are suffering from, is the best proof of 

 the infectious or contagious nature of a complaint. An 

 animal escaping an attack, when such affections are 

 raging in the locality in which it is placed, may arise 

 from a variety of causes, as non-suscej)tibility, and also 

 the possibility of the exciting agents never having been 

 brought within its sphere of inhalation. For although 

 each victim to a destructive epidemic may be con- 

 sidered as adding new seeds or fresh energy to the 

 malady by the exhalations arising fiom its body, we 



