The chief difficulty in the way of successful transfusion was, of course, the obstacle introduced by the coagulation of the blood. Bischoff in 1835 sought to overcome this by injecting defibrinated blood, and that solution of the difficulty was adopted by many operators, including Sir Thomas Smith, who, in 1873, used defibrinated blood for transfusing a case of melæna neonatorum at St. Bartholomew’s Hospital. The apparatus on this occasion consisted of “a wire egg-beater, a hair sieve, a three-ounce glass aspirator syringe, a fine blunt-ended aspirator cannula, a short piece of india-rubber tubing with a brass nozzle at either end connecting the syringe with the cannula, a tall narrow vessel standing in warm water for defibrinating the blood, and a suitable vessel floated in warm water to contain the defibrinated blood.” Others, too numerous to be individually named, used the same method throughout the nineteenth century and during the first ten years of the twentieth. Even in 1914 a method of using defibrinated blood was described by Moss. An objection was raised in 1877 that it was dangerous to do this, owing to the excess of fibrin ferment introduced with blood thus treated, but this did not greatly discourage its use. Then, as now, one of the chief uses of blood transfusion was found to be in the practice of obstetrics. A series of 57 cases of this kind were reported by Martin of Berlin in 1859, 43 of these having been successful. A further series of cases was collected by Blasius in 1863. He was able to report that of 116 transfusions performed during the previous forty years, in 56 the results were satisfactory. These statistics did not indicate a remarkable degree of success. Fatalities due to the transfusion had occurred, attended by the symptoms which we have now learned to associate with incompatibility of the transfused blood. At that time, however, the deaths were believed to be due chiefly to the introduction of air bubbles into the circulation, although it had been shown experimentally by Blundell in 1818, and again by Oré in 1868, that small quantities, such as might be accidentally introduced during a transfusion, produced no ill effects. Some explanation, however, was required, and so air bubbles for a long time received the blame.