52 PBACTIOE OF EQUINE MEDICINE. 



micro-organism is directly carried from one animal to another by 

 direct contact, while infection comes through the air, soil, or 

 places, not being a living body. 



Define a contagious disease. 



It is a disease due to a specific cause, capable of being repro- 

 duced in the body, and of being directly transmitted from the 

 sick to the well; for example, glanders, small-pox. 



What is an infectious disease ? 



It is one which is due to a disease germ introduced into the 

 economy from without, but not capable under ordinary conditions 

 of being reproduced in the body, hence not communicated from 

 one animal body to another, as influenza, tubercle. This is some- 

 times called a miasmatic disease. 



Diseases are spoken of as communicable and noncommu- 

 nicable. The communicable are divided into two classes — the 

 specific, as glanders and small-pox, and the septic, as erysipelas. 

 Communicable diseases are those that have existed in an animal 

 body before. 



The noncommunicable diseases are caused by morbific agents 

 which do not come from an animal body, but have their origin 

 in a place or thing, as malarial fever, yellow fever in the human 

 subject. 



Define a specific infectious disease. 



It is one caused by a single species of micro-organism which 

 multiply in the animal body, producing general or local symptoms 

 nearly the same in every case; that is, these organisms always 

 produce the same disease. 



Contagion spreads how? 



Principally by absolute contact with the poison, by inocula- 

 tion, by food or water, through excreta, by stable utensils, etc. 



Define a sporadic disease. 



It is one that occurs in isolated cases — that is, where a disease 

 of an infectious or contagious nature manifests itself in one animal. 



What is an enzootic disease? 



This term comes from the Greek en, " in," and zoon, " an 

 animal." 



It is where a number of cases occur in a limited locality, due 

 to the same cause. 



