INTRODUCTION. 
IN these times. of severe depression, depression which is certainly very 
strongly felt by agriculturists, and those who are tonnected 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 oanaeee an 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 
