It is becoming increasingly evident that the group termed "the hemorrhagic diseases" includes a large number of abnormal conditions, and that, at the present time, it is a fruitless task to attempt to unravel the various entities embraced by the clinical conditions which are assembled under this general head. This is due partly to the fact that the physiology of the coagulation of the blood is still incompletely understood, partly because of the impossibility of analyzing the various factors concerned in coagulation, and in part because these hemorrhagic states have been incompletely observed from a clinical point of view. Indeed, the knowledge and the methods which are at our disposal have by no means been fully and intensively applied to solving the problems which these cases present.
There are two hemorrhagic states which stand out in relief—true hemophilia of the hereditary type, found almost exclusively in males and