The fact that the coagulative principle is closely associated with the euglobulin fraction of the blood is of clinical as well as of theoretical interest. It enables us to prepare a hemostatic containing about 2 per cent of protein which is more potent than the whole serum containing 6 to 7 per cent of protein. A preparation of this kind has been made in this laboratory from horse serum and employed during the past few months in numerous cases of bleeding. This euglobulin is absolutely sterile, as it has been passed through a Berkefeld filter, and is safeguarded against decomposition by the addition of 0.3 per cent tricresol. A detailed account of the therapeutic use of euglobulin will be reported elsewhere. It may be stated, however, that it has been employed in the various manifestations of intractable hemorrhage in which horse serum has been so largely resorted to of late years, and that in certain cases has seemed to bring about most satisfactory results; in no instance has there been any untoward effect. When intravenous injections are resorted to, euglobulin seems to be preferable to serum which contains fully three times the quantity of protein. It also seems to be absorbed more quickly from the subcutaneous tissues. In all probability it will be found to meet the same indications as whole serum, possessing the advantages of concentration, and necessitating the introduction into the body of a much smaller amount of foreign protein.