The Vet. Book 



spoken of as its aetiology, and the differential 

 characters of closely-allied maladies comes under 

 the title of differential diagnosis. 



The term enzootic is applied to disease affecting 

 a number of animals within a limited area, whereas 

 epizootic-diseases are spread over a much wider 

 area, thus, for instance, influenza frequently assumes 

 both these characters, whilst swine fever may exist 

 either as an enzootic or as an epizootic. The most 

 serious epizootics, affecting animals, have ceased 

 to exist in this country. These were murrain (or 

 cattle plague), contagious pleuro-pneumonia and 

 foot and mouth disease ; and, if it were not for 

 the stringent legislative measures adopted against 

 the importation of foreign cattle into this country, 

 agriculturalists would soon suffer by the re- 

 importation of these diseases, which are constantly 

 present in such countries as Russia, Germany, etc. 

 The meaning of the terms infection and contagion 

 must be clearly understood. An infective disease 

 is one that may be communicated, directly or 

 indirectly, from one animal to another, either 

 belonging to the same or to a different species. 

 The method of infection varies. It may be that 

 the poison is distributed through the air. If so, it 

 is spoken of as volatile ; whereas, if incapable of 

 distribution in this manner, it is known as fixed, 

 and a medium for its transference is through some 

 agent — animate or inanimate ; for instance, the 

 virus may be conveyed by the clothing of man or 



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