338 CIRCULATION OF NUTRITIVE FLUID. 



of any change in the heart's action. This principle has long been 

 known, and has been expressed in the concise adage, "Ubi stimulus, 

 ibi fluxus ;" which those Physiologists who maintain that the Circu- 

 lation is maintained and governed by the heart alone, cast into un- 

 merited neglect. 



601 . An undue acceleration of the local circulation, arising from an 

 excess of functional activity in the part, and unaccompanied by any 

 other change, constitutes the state known as active congestion, or deter- 

 mination of blood. This may be artificially produced by the applica- 

 tion of gentle stimulants ; and it is usually the first change that occurs, 

 when their action proves sufficiently violent to produce Inflammation. 

 From that state, however, it is distinguished by this important charac- 

 ter, that there is merely an exaltation of the natural function, but no 

 change. Moreover we shall presently see that, in Inflammation, there 

 is a stagnation of blood, not an acceleration. We frequently meet 

 with cases, in which this active congestion becomes very manifest ; 

 especially in persons of active minds, who exert their mental powers 

 too violently, and who thereby induce an habitually-increased flow of 

 blood towards the head, manifested in the increased pulsation of the 

 carotids, the suffusion of the face and eyes, and the heat of the surface. 

 The balance of the circulation being thus disturbed, there is almost 

 invariably a diminished energy of the movement of blood in other 

 organs, especially the extremities ; as indicated by their habitual cold- 

 ness and lividity. In the treatment of such a state (which is often 

 the precursor of serious disease), it should be our object to restore the 

 circulation in the extremities, by friction, exercise, &c. ; and to abate 

 the flow of blood towards the head, by restraining the functional activity 

 of the brain, by the application of cold to the surface, by keeping the 

 head high during sleep, and other means of similar tendency. 



602. There is another condition of the capillary circulation, also 

 known under the name of Congestion, .which is precisely the opposite 

 of the preceding. In this state, there is deficient functional energy in 

 the part, and the circulation through it is consequently retarded, as 

 in the lungs where there is a partial obstruction to the aeration of the 

 blood. The same cause produces a deficient tonicity of the Arteries, 

 and allows their walls to be unduly distended by the vis a tergo of the 

 blood ; and consequently there is a great accumulation of blood in the 

 part, with a retarded movement. This condition, like the preceding, 

 predisposes to Inflammation, although in a different mode, as will be 

 explained hereafter ( 631). It is relieved by causes which promote 

 the action of the part ; thus congestion of the lungs, occasioned by the 

 effusion of fluid into the air-cells, which creates an obstacle to the aera- 

 tion of the blood, disappears when that effusion is absorbed. And 

 congestion of the liver, the result of deficient secreting power in the 

 organ, is relieved by mercurial and other medicines, which promote the 

 flow of bile by stimulating the growth of the hepatic cells. 



603. The Capillaries, like the Arteries, possess a power of contrac- 

 tion and dilatation, which seems to be very much under the influence of 

 the Nervous System, and particularly of that part of it which conveys 

 the influence of the Emotions. We have a visible example of this in- 



