Causes of Iiiflamination. 259 



of foreign bodies, parasites, infectious substances, poisons and ther- 

 mic influences which arc spoken of as external eaitses. These 

 do not act in reahty as the immediate causes of the process but 

 produce primarily some type or other of tissue change, as necroses, 

 degenerations and injuries, and the inflammatory reaction is di- 

 rectly due to an effort to compensate for these latter. 

 [It is not the heat of the flame or the steel of the knife which 

 actually causes the inflammation ; these are probably at once with- 

 drawn. They, however, alter the cells and tissues, and the inflam- 

 matory reaction arises in reality to eliminate or isolate these altered 

 structures and prevent their acting as irritants, and to make re- 

 pairs for their loss..] One and the same influence, depending upon 

 the intensity and duration of its operation, may be responsible for 

 a number of types of tissue alteration; an irritant poison, an acid, 

 may in different degrees of concentration, heat or cold, give rise 

 perhaps to a simple hyper?emia, to a superficial inflammation or to 

 deep ecshars. Strictly speaking tissue necrosis is always produced, 

 sometimes only superficially, affecting only epithelium and vascular 

 endothelium and essentially microscopic in extent, at other times 

 extending more deeply or involving decidedly larger areas and ap- 

 preciable to the unaided eye. In the first instance reparation is ac- 

 complished so quickly b}- phagocytosis and prompt regeneration that 

 the full picture. of inflammation is not developed, these two factors 

 of inflammation alone occurring in the tissue; in case of the de- 

 struction of a larger amount of tissue, however, provided it is not 

 fatal directly or from complicating infection and putrefaction, the 

 inflammatory reaction with its entire group of phenomena results. 

 A given infectious agent may in one case give rise to a rapid general 

 infectious process with fatal termination or in another only to a 

 typical local inflammation, as illustrated by the varying effects of 

 bacillus anise pticus in the virulent or attenuated state and in the 

 particular state of individual predisposition of the subject. In reality 

 the animal body reacts to all physical and chemical injuries by the 

 production of an inflammatory process, provided time be afforded; 

 that is. provided the injury does not involve a vital tissue or organ 

 to such a degree as to immediately produce death from the func- 

 tional disturbance. Where bacteria of extreme virulence, with 

 haemolytic power and capable of rapid extension, invade the sys- 

 tem, a bacteriasmia or toxic infection is said to exist ; in such cases 

 there is not enough time permitted for compensation by an inflam- 

 matorv reaction for the disturbances occasioned. Were the micro- 

 organisms of lower virulence, did they multiply more slowly at the 



