This paper is an attempt to place before dermatologists an analysis of the purpuric and allied manifestations of the skin and mucous membranes. This analysis will include a classification of purpura from dermatologic and hematologic standpoints. A brief description of the comparative histology is given. In addition, the use of venom as an aid in the diagnosis, classification and prognosis as well as in treatment of these conditions is proposed. BASIC ELEMENTS OF PURPURIC MANIFESTATIONS Purpura is essentially a hemorrhage into the skin or mucous membranes. The various terms employed, such as petechiae, ecchymoses, purpura, hematoma, black and blue spots, vibex and suffusion, are quantitative and qualitative descriptions of this hemorrhage. The definition of these terms as they are understood in our presentation is as follows: 1. Petechiae: Minute hemorrhages from the size of a pinpoint to that of a pinhead in the skin or mucous membranes.