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.
This great stride forward in the technique of blood transfusion coincided so nearly with the beginning of the war that it seemed almost as if foreknowledge of the necessity for it in treating war wounds had stimulated research. Yet during the first two years of the war almost nothing was known in the British Army of its possibilities. I have no evidence that the French or German army doctors were any better informed than ourselves. Some attempt was made in 1916 to introduce the use of direct transfusion through cannulæ, but the technique was too difficult and uncertain for the stress of war conditions. It was not until 1917, when the British Army Medical Corps was being steadily reinforced with officers from the United States of America, that knowledge of blood transfusion began to be spread through the Armies. A conspicuous part was borne by Oswald Robertson in introducing the use of the citrate method, and to him a very large number of men indirectly owe their lives. In some armies the paraffined vessel of Kimpton and Brown remained the favourite method, but to me the citrate method seemed the more suitable, because of the certainty with which success could be attained, and the same view was taken by many others. At the same time the investigators appointed by the Medical Research Committee attempted to elucidate the problems connected with hæmorrhage and wound shock, and their results, as will be seen, served to confirm the estimate already being formed of the value of blood transfusion.