118 WILLIAM HARVEY 



or heat, or any horror of a vacuum, or any other cause 

 yet indicated. 



If the finger be applied over the artery as it is pulsating by 

 the edge of the fillet, at the moment of slackening it, the 

 blood will be felt to glide through, as it were, underneath 

 the finger; and he, too, upon whose arm the experiment 

 is made, when the ligature is slackened, is distinctly con- 

 scious of a sensation of warmth, and of something, viz., a 

 stream of blood suddenly making its way along the course 

 of the vessels and diffusing itself through the hand, which 

 at the same time begins to feel hot, and becomes distended. 



As we had noted, in connexion with the tight ligature, 

 that the artery above the bandage was distended and pulsated, 

 not below it, so, in the case of the moderately tight bandage, 

 on the contrary, do we find that the veins below, never above, 

 the fillet, swell, and become dilated, whilst the arteries 

 shrink; and such is the degree of distension of the veins 

 here, that it is only very strong pressure that will force 

 the blood beyond the fillet, and cause any of the veins in 

 the upper part of the arm to rise. 



From these facts it is easy for every careful observer to 

 learn that the blood enters an extremity by the arteries ; for 

 when they are effectually compressed nothing is drawn to 

 the member; the hand preserves its colour; nothing flows 

 into it, neither is it distended; but when the pressure is 

 diminished, as it is with the bleeding fillet, it is manifest 

 that the blood is instantly thrown in with force, for then 

 the hand begins to swell; which is as much as to say, that 

 when the arteries pulsate the blood is flowing through them, 

 as it is when the moderately tight ligature is applied; but 

 where they do not pulsate, as, when a tight ligature is 

 used, they cease from transmitting anything, they are only 

 distended above the part where the ligature is applied. 

 The veins again being compressed, nothing can flow through 

 them; the certain indication of which is, that below the 

 ligature they are much more tumid than above it, and than 

 they usually appear when there is no bandage upon the arm. 



It therefore plainly appears that the ligature prevents the 

 return of the blood through the veins to the parts above it, 

 and maintains those beneath it in a state of permanent dis- 





