INTRODUCTION. 



An elementary treatise on the pathologj' of the infectious 

 diseases of animals — a treatise that states briefly, clearly and 

 comprehensively all that is known, and excludes all that is 

 not known — has long been needed not only by the students 

 who are beginning this interesting subject, but by members 

 of the veterinary profession who, as practitioners, investigators 

 or teachers, wish to learn in the shortest time the present con- 

 dition of our knowledge. A work which supplies this need 

 will be welcomed and appreciated. 



There are few subjects more important to Americans than 

 a thorough comprehension of the infectious diseases of ani- 

 mals. An enormous amount of money is invested in the 

 domesticated animals in the United States, and the security of 

 this investment depends very largely upon our ability to pro- 

 tect these animals from infectious diseases. There are many 

 diseases of this class which spread among animals as smallpox, 

 bubonic plague or cholera spreads among mankind; and it re- 

 quires a thorough knowledge of all the characteristics of such 

 diseases to guard against them, to recognize them when they 

 appear or to control them. 



For a period already too long, exact knowledge of these 

 diseases has been confined to a comparatively small number of 

 men; but with the great property interests at stake it is ex- 

 tremely desirable that this information should be distributed, 

 that not only responsible officials but every practitioner should 

 share it. With not far from three thousand million dollars 

 worth of farm animals in this country, and with a single dis- 

 ease that sometimes destroys a hundred million dollars worth 



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