The convenience of using preserved blood for transfusions was first demonstrated by Robertson (1918), working at the casualty clearing stations of the Third Army, B.E.F., in 1917-18. He collected and stored blood during periods of inaction at the front and administered it during rLush times, utilizing the blood-dextrose-citrate mixture which had been devised by Rous and Turner (1916) if found to be acid, sodium bicarbonate was administered orally until the urine was alkaline before the transfusion was performed. However, this procedure was not practicable in emergencies. Within twenty-four hours after transfusion a member of the laboratory staff visited the patient to determine whether a transfusion reaction had occurred, and performed chemical tests for haemoglobin on the twenty-four-hour urine specimen passed after transfusion. If there had been a severe reaction of any type, tests for groups and cross-matching were repeated. Collection of BloodThe donors who were accepted were healthy adults of either sex between the ages of 16 and 60. They were questioned specifically for a history of venereal disease, malaria, and allergic manifestations. They were not allowed to give blood if suffering from the slightest upper respiratory infection. This precaution was employed so that the subsequent course of such a disease could not be. ascribed to loss of blood. No donor was accepted who was suffering from active manifestations of allergy, although the blood of persons having hay-fever was used when drawn during the months when they were free from symptoms. At least three hours must have elapsed since the donor had eaten before the blood was drawn. No donor was allowed to give more than 500 c.cm. of blood in two months.The collecting apparatus consisted of an Erlenmeyer flask of 1,500 c.cm. capacity in the mouth of which was a twoholed rubber stopper. Short glass tubes were fitted into the holes of the stopper. The outer end of one glass tube was attached to a length of rubber tubing connected to a rubber suction-bulb containing a valve. The other glass tlbe was connected by means of a short gum-rubber tube to a glass adapter which fitted into a needle. After the apparatus was assembled the sterile solution of sodium citrate was aspirated through the needle and rubber tubing and into the flask, and the tubing was pinched off until the needle was inserted in the vein. This minimized the tendency to clotting which occasionally occurred in the collecting-tube. The flask was calibrated with a scale on the side so that the volume of blood mixture could be measured. When the dextrose-citrate mixture was used the dextrose solution was autoclaved in the collecting-flask.The donor assumed a supine position on an examining table with the arm supported in abduction by an arm rest. The antecubital fossa was cleansed first with tincture of iodine and 4148