=Pyogenic.=--The value of vaccines and bactericidal sera in pyogenic infections, though not in universal favour, is strongly advocated by many competent authorities, and the transfusion of blood from an immunized donor suggests itself as a natural corollary. A quantity of blood taken from a vigorously reacting man and given to a debilitated patient should theoretically supply him with a large amount of the antibodies of which he stands in need. During the war it was found that transfusion enabled an exsanguinated patient better to withstand the attacks of pyogenic and putrefactive organisms in his wounds, but this was probably due to the improvement in the general circulation which resulted rather than to any bactericidal properties in the transfused blood. It is known that outside the body blood has considerable powers of inhibiting the growth of bacteria, but ordinarily it does not possess bactericidal properties. It has been claimed, on the other hand, that the best criterion of the degree of immunity in an immunized animal is the measurement of the bactericidal power of its blood. There is justification therefore for attempting to combat a pyogenic infection by the transfusion of immunized blood. This method has at present not progressed beyond the stage of preliminary trials. I have attempted it in one case, but without any obvious benefit. The patient was a middle-aged man suffering from a chronic staphylococcal septicæmia and a secondary anæmia. He received a transfusion of 650 cc. of blood from a donor who had himself just recovered from a severe infection with staphylococcus aureus. The patient’s red blood cells underwent a temporary increase in number, but no other result was observed. One series of nine cases has been recorded by Fry, and in these the results leave some doubt as to the efficacy of the treatment. Six of these patients were almost hopelessly ill with streptococcal (five) or staphylococcal (one) septicæmia, and only one of these responded to treatment. He received transfusion from an ordinary donor and two from immunized donors, who had been given five or six injections of a mixed vaccine, the maximum dose of which contained 120,000,000 streptococci. Improvement definitely followed the transfusions, and his recovery was afterwards encouraged by injections of an autogenous vaccine. The other five patients received similar treatment, but all died. The remaining three patients had chronic suppuration, one following a streptococcal arthritis of the knee, but no septicæmia, and all recovered. It cannot be assumed that these recoveries were due to the transfusions. It is stated by Waugh that he transfused nineteen cases of pyæmia of whom twelve recovered, and in these cases an ordinary donor was used. No details, however, are given, so that it is not possible to make any inferences from this.