150 ON THE STATE OF THE BLOOD AND 
(d) “ In the Veins, the flow of blood is continuous, more rapid 
than in the capillaries, but less rapid than in the arteries.” 
Section III — Influence of the Arteries on the Capillary 
Circulation. — The rapidity of the flow of blood in capillaries is 
accelerated or retarded by acceleration or retardation of the 
flow in the arteries, the latter being determined by variations 
in the width of the arteries themselves. 
Four degrees of width may be presented by those vessels, 
with corresponding degrees of rapidity of the flow of blood : — 
1st. Artery so much constricted, that there is no room for 
the passage of the blood corpuscles. 
2d. Artery just wide enough to permit the blood to flow, 
though with difficulty. 
3d. Artery nearly normal in width, with the blood flowing 
freely. 
4th. Artery much dilated, and the flow of blood stronger and 
more rapid than in the third degree. 
In the first degree of constriction, vis a lergo is no longer 
transmitted, and the direct flow of blood is arrested in the still 
pervious terminal part, and in the capillaries to which it leads: 
the constriction continuing, the blood regurgitates from the 
anastomosing arteries and from the veins, through the capillaries, 
into the terminal part of the affected artery. “ The red cor- 
puscles of the regurgitating and slowly-moving blood aggregate 
together, and in some places become stagnant.” If the artery 
resume its normal width, the flow of blood resumes its natural 
onward course, and the stagnation, if it exists, is dissipated. 
When the width of an artery is in the second degree, the 
stream may continue direct, but the circulation in the capil- 
laries supplied by that artery is sluggish ; in some, perhaps, 
stagnant. 
CHAPTER III. — Of the State of the Blood and the Blood- 
vessels in Inflammation of the Web of the Frog, from an in- 
cised Wound. 
In both congestion and stagnation, Mr. Jones says, “ it is to 
be understood that there is an unusual accumulation of red cor- 
puscles in the blood of the affected vessels.” So long as the 
blood flows, however tardily, we have congestion. When the 
blood ceases to flow, we have stagnation. In order to ascertain 
how the congestion and stagnation of blood which are occasioned 
by an incised wound are brought about, Mr. Jones instituted 
experiments and observations to determine : — 
1st. The Effect of Section of an Artery of the Web of the 
Frog on the Flow of Blood in the I art. 
When an artery is cut across, its caliber is immediately 
