[Illustration: Fig. 10.--DRAWING BLOOD FOR TRANSFUSION]
When the donor’s arm has been congested by gripping it above the elbow, or better by the application of a tourniquet[9] drawn to the requisite degree of tightness, a suitable vein, usually the median basilic, is chosen. The area of puncture is washed with ether and a very small quantity, 2 to 3 minims, of 2 per cent. novocain is introduced over the vein with a hypodermic syringe. If a larger quantity is used, the vein may become obscured, but this small amount may be dispersed by a few moments’ pressure with the finger, and is usually enough to anæsthetize the very small area of skin that is to be operated upon. A tiny cut in the skin is then made with the point of a scalpel, and the needle is pushed through into the vein. If the donor’s vein is a large one, such as is usually found in the type of donor recommended in a previous chapter, this is quite easy to do. To make it equally easy if the vein be smaller, it has been suggested by Watson that the vein may be fixed by pushing an ordinary fine sewing-needle through the skin at right angles to the line of the vein, into the vein, and out again through the skin. This needle is held with the forefinger and thumb of the left hand, while the right hand pushes the transfusion needle into the lumen of the vein just below it. When the needle is in the vein, the blood flows out rapidly through the tube which hangs into the flask containing the citrate, as illustrated. This flask is held by an assistant, who mixes the blood with the citrate by gently swinging it. If a properly adjusted tourniquet is kept on the donor’s arm while he works his forearm muscles by clasping and unclasping his hand, a flow of blood is obtained which is fast enough to prevent clotting in the needle, and indeed is quite as fast as most donors can tolerate. Blood up to 1,000 cc. may be collected in this way in ten to twenty minutes. If the vein be of a good size, it makes no difference whether the needle be inserted towards the heart or away from it. When enough blood has been collected, the tourniquet is removed, the needle is withdrawn, and pressure is maintained with a sterile swab over the site of puncture for a few minutes. No further bleeding will take place after this, and no suture is needed. The donor’s part in the operation is then finished. He should be made to lie on his back for a few hours afterwards, and given plenty of fluids, but beyond this no special precautions are necessary.