334 ACTION OF THE NERVE-FIBKES OF THE 



the point actually injured. This inflammatory blush 

 too, as can be easily proved, may be completely re- 

 moved by pressure. If I press the skin, the tint of 

 the portion inflamed will become pallid and of pre- 

 cisely the same hue as the surrounding healthy skin. 

 When I withdraw the pressure, and the blood is per- 

 mitted to return, the pallor is gone and the capillaries 

 of the normal skin are distended to precisely the 

 same calibre as before ; the dilated vessels in the seat 

 of inflammation are again dilated, and to precisely 

 the same degree as before the blood was pressed from 

 them. This simple experiment proves not only that 

 there exists some mechanism by which the calibre of 

 the vessels may be not only increased and reduced so 

 as to allow a larger or smaller quantity of blood to 

 flow through the capillaries in a given time, but that 

 the increased quantity of blood which traverses these 

 tubes in inflammation is determined and regulated 

 by the degree of contraction maintained by the mus- 

 cular fibre-cells of the small arteries. The particular 

 state of contraction can be kept up only through the 

 instrumentality of nerves and nerve-centres in which 

 a certain temporary change has been established and 

 is maintained for a time. Such an arrangement as 

 that described in page 327, would enable us to ex- 

 plain the facts above referred to. 



In the early stages of inflammation probably more 

 blood actually flows through the capillaries of the 

 inflamed part than through those of the healthy 

 tissues ; but after a time, as is well known, the cir- 

 culation becomes slower, the capillaries are distended, 

 and at last the blood ceases to flow. The self-regu- 

 lating mechanism fails to act, and, unless relief 

 speedily follows, may be destroyed. 



Inflammation, 'as it occurs in the tissues of the 

 higher animals is an exceedingly complex process, in 

 which vessels, nerves, and many other structures take 

 part. But changes are also occurring during in- 



