INTRODUCTION. 



An elementary treatise on the pathology of the infectious 

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

 comprehensi\-ely 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 veterinarj' 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 animals. 

 An enormous amount of money is invested in the domesticated 

 animals in the United States, and the security of this invest- 

 ment depends very largely upon our ability to protect these 

 animals from infectious diseases. There are many diseases of 

 this class which spread among animals as smallpox, bubonic 

 plague or cholera spread among mankind ; and it requires 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 re.sponsible 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 disease 



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