INTRODUCTION. 



In these times of severe depression, depression which is certainly very 

 strongly felt by agriculturists, and those who are connected with agriculture, 

 no subject in the nature of an introduction to a work dealing with the more 

 common diseases of the domesticated animals, is more likely to prove of 

 interest and value, than a plain exposition of some of the erroneous views, 

 which are commonly held with respect to the nature, prevention and curability 

 of certain maladies. The knowledge of the phenomena of disease among 

 those who have not carefully studied them, must necessarily be far behind 

 that of the skilful specialist, who advances with the genius and spirit of the 

 times. Some of the opinions held by the public are a source of much evil ; 

 in many instances these errors have been impressed on the minds of the 

 people by their leaders in past generations, and now the uprooting of them 

 proves a slow and tedious process, which still bars the path of progress. 



When the historian of the future takes in hand to record the wondrous 

 discoveries made in this latter half of the nineteenth century, he will have a 

 very pleasant and a very lengthy task ; for they have truly been great and 

 marvellous. In the field of practical science, the development of our 

 knowledge of the marvellous and varied properties of electricity, and the 

 inestimable value of these discoveries in everyday life, will no doubt attract 

 deep attention. 



In human and veterinary medicine, the elaboration by Pasteur and 

 others of the germ theory of disease originated by Astier, Schwann, and 

 Cagniard-de-Latour in the first portion of this century, marks one of 

 the most important epochs in the history of these sciences. The influence 

 exerted by these discoveries is immense. Almost equally great is the 

 revolution in the modes of treatment of disease, and this is to be attributed 

 partly to that particular practical contribution to the subject of antiseptic 

 measures for which we are principally indebted to Sir J. Lister. 



These points hold equally with regard to animals and to man. It is not 

 too much to say that the light, which is thrown by the two departments of 

 medical enquiry on each other, is daily becoming more and more thoroughly 

 recognised. 



The microscope has revealed the nature of the 'poison,' or 'contagion,' 

 or 'virus' of the contagious fevers of man and animals; and it is now known 

 that each of the specific fevers runs a more or less definite course, presenting 

 special peculiarities, by which it may be recognised, in accordance with the 



