PATHOLOGY 79 



Inflammation 



Definition. — Inflammation is the protective and curative re- 

 sponse of any tissue to an injury. It is a complex pathological 

 process consisting of disturbances of circulation, and construc- 

 tive and destructive tissue changes. Pain, heat, redness, swell- 

 ing and impairment of function are the symptoms of inflamma- 

 tion. These may be slight and not evident in mild and chronic 

 inflammation. 



The changes which occur in the blood vessels during inflam- 

 mation as in pneumonia for example are : ( 1 ) dilation of small 

 arteries, capillaries, and veins; (2) increased current velocity at 

 first, then decreased; (3) obstruction of the blood current, due 

 to the collecting of corpuscles in the capillaries and small veins, 

 and the adherence of white corpuscles to their walls; (4) when 

 the velocity of the blood begins to decrease, both kinds of cor- 

 puscles and the blood plasma may pass through the walls of 

 small veins and capillaries, i.e., exudation. Thus the bronchioles 

 and air cells become filled in a case of pneumonia. 



The changes in an inflamed tissue, the udder for instance, are 

 variable. In the beginning of an inflammation, the causing 

 agent produces cell degeneration, and in some instances cell 

 death, whereas in the later stages of inflammation there may be 

 cell multiplication and regeneration of tissue as in the healing 

 of a wound. 



Inflammation varies according to (a) resisting power of tis- 

 sue, (b) activity of cause, (c) length of time the cause is in 

 action. 



Causes of inflammation. — Inflammation may be caused by 

 mechanical injury, such as barb-wire cut ; by chemical action as 

 in careless burn of the skin by caustic potash, in dehorning 

 young calves; by excessive tissue activity, e.g., a badly over- 

 worked kidney caused by an overdose of turpentine ; injury by 

 extremes of heat and cold, or by toxins from bacteria or from 

 dead tissue. Inflammation thus caused has little tendency to 

 spread beyond the part injured, and there is usually little or no 

 pus unless germs invade the inflamed area. 



"Microbes," "microorganisms," "bacteria," and "germs" 

 are synonymous terms as commonly used. These can cause 

 inflammation without the aid of other local injury as for ex- 

 ample, a suppurative (pus) inflammation of glands in the throat 



