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. In this way a large number of operators in this country became familiar with the various methods, and transfusion has in consequence been used increasingly in civilian practice since the war. It is undoubtedly destined to figure still more largely in the therapeutics of the future. Meanwhile the public mind is becoming gradually more used to the idea, and the time is past when every transfusion is deemed worthy of a sensational headline in a newspaper. Nevertheless, at the end of the year 1920 the following advertisement appeared in the personal columns of _The Times_: “Will any Doctor who knows method of treating cancer by transfusion of child’s blood kindly write Box --.” So the wheel is come full circle, and the shade of Pope Innocent VIII may well chuckle as he notes the small advance in popular knowledge since the fifteenth century. CHAPTER II INDICATIONS FOR BLOOD TRANSFUSION The indications for blood transfusion are gradually becoming more numerous as experience of its effects accumulates, and there can be no doubt that the value of transfusion as a therapeutic measure is destined to become much more generally recognized than it is at the present time. Lack of knowledge, together with an exaggerated idea of the difficulties of the process, is the chief obstacle to its more extended use. Time and the education of the rising generation will provide the remedy for this.