CHAPTER II. 

 INFLAMMATION. 



DEFINITION. — Inflammation is not a simple process. 

 Many pathologists have ceased to define it. It is now asso- 

 ciated with such a complex series of symptoms that it is no 

 longer an entity. According to Stengel, inflammation is a 

 series of changes which occur in living tissue, which are des- 

 ignated the vascular, exudative, degenerative, and regenera- 

 tive as a result of irritation by chemical, mechanical, or ther- 

 mal agents, — the most common being toxic, due to the pro- 

 ducts of pathogenic bacteria. In other words, inflammation 

 is the reaction of tissue to injury. Clinically, the phenomena 

 of inflammation, as expressed by Galen, consist of tumor 

 (swelling), rubor (redness), calor (heat), and dolor (pain), 

 to which has been added functio Isesa (impaired function). 

 Its study not only includes the acute processes caused by bac- 

 teria, other fungi and protozoa, but the remote changes which 

 occur as secondary reactions. Hence it will be seen that a 

 large part of special pathology is included under this head- 

 ing. Even some pathologists believe that tumors are of this 

 origin. Malformations can hardly be excluded, for most of 

 them are due to injurious agents acting upon the embryo and 

 influencing or preventing development. In this chapter we 

 shall attempt to give only a general description, principally 

 microscopical, of the most common conditions found in do- 

 mestic animals which are produced by either pathogenic bac- 

 teria or other injurious agents. 



ETIOLOGY. — Bacteria are by far the most common 

 cause of inflammation. The mere presence of these small 

 vegetable cells in the tissue produces little or no change; but 



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