Z BOVINE PATHOLOGY. 



mal state. Alteration of structure as present in disease 

 is often brought about by changes from ordinary states of 

 parts in situation, relations (either among themselves or 

 with foreign bodies), and form. Such changes may result 

 occasionally from inherited and other intrinsic influences, 

 but are almost always due to agency from without. Every 

 living being is adapted to certain external conditions, and 

 is capable of undergoing modification in accordance with 

 any variations which these conditions may show within 

 certain limits , but the complexity of organisation in such 

 an animal as the ox requires gradual transitions, or dis- 

 order ensues. Thus, we generally seek the cause of any 

 attack of disease in changes of surrounding agencies, as 

 weather, food supply, &c. This branch of study is termed 

 Etiology. 



Causes are predisposing or exciting. The greater the 

 amount of activity in a part or animal the greater the 

 liability to disease. Thus may be explained a number of 

 facts, such as that highly organised animals are most 

 often diseased, when we develop one system specially for 

 economic purposes it most frequently of all the body 

 systems is liable to disorder, and the most active body 

 tissues are similarly susceptible. But a part may be in such 

 a highly active condition and yet able to do its duties, until 

 some sudden change disturbs its relations with surrounding 

 parts and alters its structure. These states of verging on 

 disease are termed Predisposing Causes. Thus, the milch 

 cow is predisposed to mammitis, and the fattening ox to 

 diseases of the digestive apparatus. By an extension of 

 meaning, predisposition has come to imply also liability to 

 disorder from any external surrounding conditions ; thus, 

 we hear of predisposition to choking in the fact of animals 

 being fed on improperly prepared turnips, and to hair 

 accumulations in the rumen, as a result of the habit oxen 

 have of licking themselves and each other. Determination 

 of all predisposing causes present is highly necessary, for 

 counteraction of them is essential to success in treat- 

 ment. 



By some authorities intrinsic causes are termed Predis- 



