It has been customary with authors to describe under the general heading Purpura a number of affections presenting as a common symptom the extravasation of blood into the tissues, more especially of the skin and mucous membranes, quite irrespective of etiological or pathological considerations. Thus, the tiny ecchymoses caused by the bites of fleas have been denominated purpura pulicosa; the larger bruises resulting from external violence, purpura traumatica; the extravasations occurring in the course of scurvy, purpura scorbutica; those encountered in malignant small-pox, purpura variolosa; and so on. These affections, differing widely in nature, possess as a common symptom the escape of blood from the vessels into the tissues. It is evident, therefore, that in the sense often employed the term purpura is used to describe a symptom or symptoms common to a variety of non-related maladies. If there be a peculiar morbid process having for its constant and characteristic symptom the spontaneous escape of the blood from the blood-vessels, it is plain that interstitial hemorrhage from external violence or from the action of a definite poison circulating in the blood and disorganizing it and its containing vessels, as in phosphorus-poisoning, or from the influence of certain zymotic diseases, should not be designated by the title properly belonging to a substantive malady. The question, therefore, is: Are there groups of symptoms indicating morbid action of definite character, but of varying intensity, to which the name purpura may with propriety be applied?