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DIFFERENCES IN THE EFFECTS OF ABSTRACTING 
ARTERIAL AND VENOUS BLOOD. 
By Mr. War drop. 
The abstraction of blood is employed as a remedial means, 
either for the purpose of diminishing the action of the heart and 
arteries in inflammatory diseases, or for the removal of a surplus 
quantity of the sanguineous fluid, whether venous or arterial, in 
particular organs wherein there is what has been called “ plethora/' 
or a congestion of that fluid. A quantity of blood may also be 
abstracted in some diseases where the qualities of the body have 
become changed ; but, whatever explanation may be given of the 
effects of blood-letting, there is no doubt of its multiplied results 
in the treatment of disease, whether the fluid be removed from 
the system by art or by a “ spontaneous hemorrhage." 
Blood may be abstracted either from the venous or from the 
arterial system ; but I am not aware that much attention has 
been paid to distinguish the difference of the effects that are 
produced on the system by taking blood from an artery and from 
a vein, though it can readily be conceived that such difference 
may be considerable. The chief reason which is usually given 
for opening arteries in preference to veins has been, that the 
blood may be "obtained more directly from a particular part, and 
in larger quantity, and more promptly, than it would be by open- 
ing a vein : but as almost the only vessel on which arteriotomy 
has been performed is the temporal artery we know little of th 3 
effects of abstracting arterial blood, except when it has been taken 
from that vessel. The result of my own experience has been 
unfavourable to arteriotomy ; having found that the inflamma- 
tory symptoms recur much more frequently after a certain quan- 
tity of blood has been removed from an artery than if an equal 
quantity have been taken from a vein in the arm; and I know 
that this observation coincides with the experience of some others. 
There are, however, cases where the difficulty or even impos- 
sibility of procuring the requisite quantity of blood from a vein 
renders arteriotomy an indispensable and important operation for 
the abstraction of blood. 
A little reflection on these two modes of bleeding may, to a 
certain degree, explain how this difference of effect is produced. 
When blood is abstracted from an artery there must be an 
immediate diminution in the supply of blood to the part nourished 
by that artery ; but such is the vigour of the anastomosing 
branches, that the supply of blood thus cut off is very quickly 
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