Blood Letting
a method of relieving the human system in states of genera eneral or local plethora by the abstraction of blood. General plethora is best treated, according to this method, by withdrawing a considerable quantity of blood from the arteries (arteriotomy) or veins (venesection). Local engorgement, or hyperæmia, of a part is usually treated by abstracting blood from the smallest sized vessels, or capillaries, present in the skin, by the methods of scarification or leeching. In these cases, the removal of blood from the superficial textures diverts the blood stream in part from underlying tissues, and thus reduces the tendency tendency to inflammatory action in the latory deeper structures. In general blood letting the object is to reduce the strength of the blood stream throughout the whole system, and thus to diminish the acuteness of feverish conditions. The most usually employed method of accomplishing this is by the opening of one of the superficial veins of the arm, and allowing a sufficient quantity of blood to escape from the blood vessel thus operated upon. The amount of blood actually abstracted in blood letting must depend on the age of the patient and the nature of the case. The operation would be the case.
The operation would be scarcely necessary if less than a quarter of a pint is to be removed, and it is now rare to remove more than one pint at one operation, however severe the case in which it is employed. See BLEEDING.