r6 



The actual and immediate causes of inflammation are such 

 causes as modify the molecular state of the tissues, and arrest 

 for the time the usual interchange of material between the 

 tissues and the blood. This induces a true inflammation. 



An example of the three stages or processes of stimulation, 

 irritation, and inflammation, may be very well studied in the 

 action of a common mustard plaster applied to the skin. 

 Its first effect (or the only one), if the mustard be diluted, is 

 merely stimulant, the skin grows warmer and redder and its 

 sensibility is moderately heightened. If it be strong and 

 allowed to remain, irritation is produced ; this is shewn by 

 pain, tenderness on pressure, &c. If the irritating matter 

 be now withdrawn, all of these may subside without going 

 further. But if the irritation be continued up to a certain 

 point of duration, and intensity, inflammation occurs, then 

 we have redness, heat, pain and swelling, with effusion of 

 lymphj which in the cutaneous inflammation caused by a 

 sinapism or plaster of cantharides, raises up the cuticle in 

 the form of a blister. The essential minute phenomena of 

 inflammation, as regards the circulation, are : 

 Central stasis. 

 Concentric hyperaemia. 

 Exudation. 



The actual cause of inflammation, we have said 

 already, is the arrest for the time of the usual interchange 

 of material between the tissues and the blood. 



Stimulation causes active hyperaemia. The arteries 

 under its influence exhibit reflex action. When stimulation 

 is carried to morbid excess, interrupts, by the molecular 

 disturbances it induces, the normal life-movement of the part, 

 and checks the interchange of particles going on between 

 the capillaries and the tissue, and, as a consequence, stagna- 

 tion ensues. 



Inflammation, then, may be simply defined as a local 

 lesion of nutrition, with concentric vascular excitement, re- 

 sulting in exudation. The products of inflammation by 

 exudation are — 



Serum, Blood, Mucus, Lymph, 



The inflammatory effusion of non-fibrinous serum is rare. 

 The term is often applied, however, clinically to a serosity 

 which contains a small proportion of fibrin, as in the effusion 

 which follows pleurisy. 



Blood is exuded occasionally only ; e.g., in dysentery, in 

 nephritis, and (dissolved) in pneumonia. 



