The question of the amount of blood to be withdrawn must be settled at the time and for each individual case. The pulse is watched, as well as the patient’s face; the best indications when to cease being noted in this way. From 500 to 1000 Cc. may be removed according to the condition of the patient and the degree of emergency. While the operation is a trifling one, it should, nevertheless, be performed with strict aseptic precautions. One of the veins at the bend of the elbow, usually in the left arm, is commonly chosen, although in rare instances, when there is intense cerebral venous congestion, the external jugular may be selected. At the elbow the median basilic vein crosses the brachial artery, being separated from it only by a thin prolongation of the biceps tendon. It was especially in opening this vein at this point with the old-fashioned lancet, which was plunged perpendicularly to the surface and directly into the vein, that injury to the artery occasionally occurred, thus leading to varicose aneurysms and aneurysmal varices. The skin should be thoroughly cleansed; a reasonably tight constriction is made about the middle of the arm by a bandage, not so tight as to completely occlude the radial pulse; the arm is allowed to hang downward and the patient encouraged to grip some object in order to better fill the vein. This soon becomes prominent, after which an oblique incision is made through the skin above it, so that the vessel itself is exposed. Then with a sharp bistoury the external surface of the vein is pricked with the point, and a cut made outward. The opening in the skin should be free; the skin may be frozen, or in very sensitive patients local anesthesia may be first produced with cocaine. By tightening and releasing the grasp, that is by closing and opening the hand, the flow of blood may be hastened. When it is time to cease, the bandage should be removed and an aseptic pad be applied over the site of the wound, suitable pressure being made, and the arm kept at rest for two or three days. When the jugular or some other vein is selected the procedure is essentially the same. =Arteriotomy.=--Arteriotomy, or the opening of an artery for bloodletting purposes, is resorted to only in rare instances, and in an emergency. The temporal artery is the one usually selected because of its accessibility and the ease with which its outflow can be controlled. Its position is determined by its pulsation; it should then be exposed by incision through the skin, and opened exactly as is a vein, _not cut through_, lest it retract and furnish an insufficient amount of blood. It should, however, be divided and tied before application of the dressings.