Simplification of the group tests soon followed, as is described in another chapter. At the same time great improvements were made in the use of syringes, paraffined tubes, and in anastomosis of the blood-vessels. In this connexion one of the most notable contributions was made by Curtis and David, who in 1911 introduced the use of syringe transfusion through a two-armed tube coated on the inside with paraffin. In 1913 indirect transfusion by means of the paraffined vessel was introduced by Kimpton and Brown, and it was now evident that blood transfusion was shortly to become a method of treatment which would be without any very difficult technique, and could therefore be more extensively applied. The final advance was made in 1914, when the use of sodium citrate as an anticoagulant was made possible by the work of Lewisohn in America, of Hustin in Belgium, and of several others, who all arrived independently, but almost simultaneously, at the same conclusion. The use of an anticoagulant was no new idea. In 1858 the use of small quantities of ammonia had been suggested by B. W. Richardson in the _Guy’s Hospital Reports_, and in 1869 sodium phosphate was used in four obstetrical cases by Braxton Hicks, who found that the process was greatly facilitated thereby; but neither of these methods came into general use. It had long been known that hirudin or leech extract, and the salts of oxalic acid or of citric acid, could be used as anticoagulants outside the body, but their supposed toxicity had prevented their being used for transfusion. The proof that sodium citrate was both efficient for this purpose and non-toxic in a dilution that was still effective at once raised blood transfusion to a wider sphere of usefulness than had been possible before. The first transfusion of citrated blood was performed by Professor L. Agote of Buenos Aires, on November 14, 1914, a date which is therefore of the greatest importance in the history of blood transfusion. A method had at last been discovered which approached the ideal, since it united the four cardinal virtues of simplicity, certainty, safety, and efficiency.