INFLAMMATION. 



connection with the stagnation of blood in it ; for, if we expel the blood 

 from the ear of » rabbit, for example, and keep the part, by ligature or 

 other means, bloodless for some time, inflammation will be set up in it, 

 on the blood being again allowed to fill the vessels. 



As the filtering power of the walls of the capillaries varies inversely as 

 the blood pressure in them ; the exudation of inflammation is rich in fibrin- 

 producing material and leucocytes, and is consequently liable to coagulate 

 in the tissues if allowed to remain in them. The result of this coagulation 

 will be the formation of fibrous bands (adhesions), which will, more or less, 

 interfere with the movement of the part. The swelling will also lower the 

 vitality and strength of the part by impeding its circulation. The most 

 rational means for the removal of the exudation is massage (p. 675) and 

 external pressure (for an example see page 44), which may be increased 

 considerably beyond that which had existSi in health. During the course 

 of unchecked inflammation, the blood pressure on the walls of the capillaries 

 causes these vessels to increase greatly in size. In fact, granulations (the 

 small, rounded excrescences of " proud flesh ") in a wound, consist of 

 bunches of abnormally distended capillary loops. 



(Edema (the accumulation of fluid beneath the skin) may also result from 

 passive congestion, especially when the part has been weakened by previous 

 attacks of inflammation, as in the case of the filled legs of horses which 

 have done a good deal of work. 



Inflammation is generally characterised by pain, heat, swelling, and, if the 

 skin be thin and white, redness. The pain is due to pressure on the nerves 

 of the part ; and the swelling, as we have already seen, to the exudation 

 of lymph. The redness, and the heat, which, according to John Hunter, 

 is never in excess of that in the interior of the body, are caused by the 

 presence of an increased supply of blood, as in blushing, for instance. 



REPAIR AFTER INPLAMDVEATION.— The leucocytes which escape from 

 the capillaries into the tissues during inflammation, appear to be of two 

 kinds, namely, one which supplies fibrin-ferment to the exuded plasma ; the 

 other which devours dead matter and invading disease germs. These 

 scavengers, having absorbed into their substance waste and hurtful material, 

 may, if few in number, be carried away by tho lymphatics. If they are too 

 numerous — by reason of the intensity of the inflammation — for this to 

 happen, the cells of the part, after the inflammation has begun to abate, 

 may, in their turn, absorb the leucocytes which are present and any remain- 

 ing debris or germs, and may then proceed to repair the injury by scar- 

 tissue, as in wounds (p. 63). During the acute stage of inflammation, the 

 cells of the injured part seem to remain paralysed, and do not perform their 

 3ca\engering and microbe-devouring function until reaction sets in. The 

 leucocytes, on the contrary, play that role from the beginning of the 

 inflammatory process. The method of repair, just described, generally 

 takes place in. severe cases of sprained tendon and ligament, in which the 

 presence of the scar-tissue and of the coagulated exudation will be mani- 

 fested by thickening of the part. If the migrated leucocytes be in too great 

 numbers to be thus removed, they will in all probability die. When in- 

 flammation is followed by an accumulation of leucocytes and of plasma 

 which does not coagulate, the result is a white or creamy liquid called pus, 

 and when the surrounding tissues are involved, so that a cavity develops 

 containing pus, we have what is termed an abscess. The plasma (serum) 

 of pus does not coa,gulate because it is devoid of fibrinogen. Although pus 

 may be an innocuous fluid when it is produced by leucocytes, it is usually 

 of bacterial origin, in which case it contains bacteria that excrete a sub- 

 stance which causes the pus to have a corrosive action on the tissues ; 

 hence, the necessity for the destruction of these bacteria and the removal 

 of the pus. An ulcer may be compared to an open abscess, and the 

 granulations formed in both cases, are the result of an attempt to repair, 

 made by the attacked tissues. 



