Among the various pathologic conditions in which an augmented tendency to hemorrhage is apparent, the special disorder known as hemophilia has certain unique features. Its hereditary character is conspicuous; indeed, as Wells 1 has remarked, since hemophilia seems, superficially at least, to depend on some alteration in a chemical property of the blood, namely, coagulability, it is frequently regarded as an example of hereditary transmission of chemical abnormality. Characteristic, uniformly present structural anomalies have not been discovered in hemophilic persons, so that etiologic explanations must be sought elsewhere. The incidence of hemophilia exhibits some analogy to the occurrence of chemical abnormalities of metabolism, such as cystinuria, alkaptonuria and pentosuria, so far as the hereditary features are concerned. It has been termed "the most hereditary of all hereditary diseases."
It is obviously of no small importance to discover the factors responsible for the condition of the blood in hemophilia. The bleedings,