28 CLASSIFICATION OF DISEASE. 



comprehends and includes all of tlie principal diseases of our 

 animals wliicli are spoken of as epizootic, enzootic, infectious, 

 contagious, or specific : all those which we believe due to 

 peculiar telluric or meteorological conditions, to the noxious 

 emanations from decaying animal or vegetable matter, and 

 those depending upon specific disease poisons, whatever these 

 may be, capable of passage and of propagation from one living 

 organism to another, and in that passage and propagation 

 capable of infinite multiplication, and communicable by direct 

 contact, or indirectly through various channels of communica- 

 tion and association, contaminating food supplies and drinking 

 water or infectiuGr the air. 



CHAPTER 11. 



OF EXOGENOUS AGENCIES, SPECIFIC AND CONTAGIOUS DISEASES, 

 AND ENZOOTIC AND EPIZOOTIC INFLUENCES. 



Seeing that in the course of the consideration of the details 

 pertaining to the practice of equine medicine there must of 

 necessity be frequent cause for the employment of the terms 

 ' contagious ' and ' infectious,' so generally employed with refer- 

 ence to diseases of all animals, before entering upon the study 

 of these affections in order and individually, it will be useful 

 to give a little attention to those terms contagion and conta- 

 gious diseases, enzootic and epizootic influences, so often in our 

 mouths. 



A contagious, otherwise specific, disease, may be defined as 

 an unnatural or morbid state of an animal body, owing its 

 existence to the reception from without of certain living 

 entities which have been developed in connection Avith an 

 animal previously in a similar diseased condition. 



The implantation of the virus or specific poison of a con- 

 tagious disease may take j)laco directly or indirectly, by inocu- 

 lation, by contact, or by emanations proceeding from the 

 diseased. 



It seems highly probable that many circumstances, operating 

 both in the diseased and the healthy, extrinsically and 



