6 METHODS OF ELUCIDATING DISEASE. 



clianges or distvirbancos. Of diseases which seem to owe their 

 existence to this are : 



(i.) Certain constitutional or blood diseases, as rheumatism. 



(ii.) Many exhibitions of arthritic disease, not rheumatic, 

 largely affecting bone tissue, as spavin and the peculiar 

 joint disease of young animals. 



(iii.) Early degeneration of organs and particular tissues, 

 generally appearing as local diseases. 



(iv.) Anatomical malformations and some diseases of special 

 sensation. 



(v.) Some affections of the nervous system, as epilepsy and 

 the so-called chorea. 



(vi.) Probably certain skin diseases, as some forms of 

 eczema. 



h. Age. — Many diseases are more apt to attack animals 

 before they reach maturity ; and special organs in particular 

 states of development, as well as particular states of certain 

 structures dependent on their age, predispose to disease. 



c. General or Constitutional Vigour. — This depending on 

 the state of activity and robustness of the whole system, its 

 general tone, and probably also its relation to present states, 

 dependent on previous disease. 



d. Breed or Variety. — Certain races of animals are doubtless 

 more susceptible of particular diseases than others. 



e. Temperament. — This influence with the horse may not be 

 so well made out as Avith some other animals ; but there are 

 fairly reasonable grounds for believing that it does exist. 



/. Idiosyncrasy or Medical Constitution. — By this is meant 

 to be indicated that some animals are, apart from obvious 

 causes, more liable to be acted upon by adverse agencies than 

 others. 



2. Extrinsic or Exogenous Influences, a. Atmos2)heric. 

 — The respirable air Avith which animals arc surrounded ever 

 exercises a certain amount of influence, even when uncon- 

 taminatcd, through its moisture or dryness, but more particu- 

 larly Avhcn impregnated with noxious emanations from living 

 animals or material given off from decaying organic matter or 

 other unwholesome gases. Its electrical condition, probabh', 

 and its excess or deficiency in ozone may also tend to induco 

 an action of a predisposing or exciting character. 



