PART II 

 COMMON DISEASES OF THE HORSE 



CHAPTER X 



DISEASE IN GENERAL 



DEFINITION AND CLASSIFICATION OF DISEASE 



Disease includes all those variations from the normal which 

 impair more or less the adaptability of the animal to its surround- 

 ings. Disease modifies existing body structures, but does not add 

 new parts to the body. 



Synonyms of the term "disease" in common use are malady, 

 affection, and complaint. The word abnormality is applied par- 

 ticularly to a structural modification like a bone spavin. A con- 

 genital fault, like that of the teeth, shown in Fig. 63, is called a 

 malformation or defect. The term deformity is used for an acquired 

 structural fault; for example, atrophy or "sweeny" of the shoulder 

 muscles. 



Pathology is that branch of medical science which has to deal 

 with all phases of disease except the treatment. It consists of a 

 study of the modifications in functions and changes in structure 

 caused by disease. 



Classification of disease on a satisfactory basis has been possible 

 only within the last thirty years, or since the study of bacteriology 

 has revealed the causes of many heretofore obscure diseases. Up 

 to that time most diseases were supposed to be due to a miasma, the 

 mist arising from marshy places. On the strength of this recent 

 knowledge we have come to recognize two great classes of disease 

 — the non-infectious and the infectious. A division into non- 

 communicable and communicable diseases is helpful in studying 

 methods of transmission and control, and will be followed when the 

 individual diseases are considered. 



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