PART II 

 COMMON DISEASES OF ANIMALS 



CHAPTER X 



DISEASE IN GENERAL 



DEFINITION AND CLASSD7ICATION OF DISEASE 



Disease includes all those variations from the normal which 

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

 roundings. It is usually accompanied by a feeling of discomfort 

 or loss of ease. Disease modifies existing body structures, but 

 does not add new parts or functional capacities which the normal 

 body does not possess. The usual capacity for work of organs 

 affected with disease may be either diminished or exalted, 

 but no new functions, forms of energy, or other capacities are 

 developed. 



Synonyms of the term disease in common use are malady, 

 affection, disorder, sickness, indisposition, ailment, and complaint. 

 The word abnormality is applied particularly to a structural 

 modification like a bone spavin. A congenital structural fault, 

 similar to that of the teeth, shown in Fig. 78, is termed a malfor- 

 mation or defect. An acquired structural fault suoh as a cocked 

 ankle, shown in Fig. 66, is termed a deformity. 



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. A clear understanding of pathology is im- 

 possible without a thorough knowledge of the normal structure 

 and functions of the body and the chemical and physical changes 

 that are constantly going on in it. The layman without this 

 complete information may recognize and correctly name such 

 common and outstanding morbid conditions as wounds, fractures 

 of bones, abscesses, galls, etc. He may even learn to treat them 

 properly through observation and instruction. However, he is 



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