XIV INTRODUCTION 



enterprises are discharged, and in innumerable ways the wel- 

 fare of people who have no part in the ownership of any of 

 these animals or their products is affected. 



Finally the most serious of all, is the case in which the 

 animal plague, in addition to being destructive to animal life, 

 is communicable to and fatal to man, as is true of anthrax, 

 rabies and tuberculosis. Such diseases destroy property, dis- 

 turb business, lessen the food supply, and directly threaten 

 human life. What more is needed to impress upon the reader 

 the supreme importance of studying and understanding the 

 infectious diseases of animals ? 



The pathology of these diseases is in itself a large subject. 

 Investigations concerning it have extended over more than a 

 century of time and the literature of the subject is enormous. 

 To concentrate this knowledge, to select the truth and discard 

 the errors, and to develop a concise and sj^stematic treatise is 

 a task of great magnitude and one which has required much 

 labor and thought. The writer has not seen the manuscript, 

 but, from his long and intimate acquaintance with the author, 

 he feels sure that the work has been patiently, carefully, intelli- 

 gently and thoroughh' done, and that it will be favorably 

 received. 



D. E. Salmon. 



