Of the several tropical diseases whose etiology is yet in question, dengue undoubtedly stands at the head of the list in importance. It has long been considered an infectious disease, as the writings of Ornstein,1Eulenberg,2Graham3and Hirsch4attest, while we find Leichenstein,5Malie,6von Duringe7and a half dozen others presenting almost indisputable evidence that it is contagious, in the technical sense of the word, as well. McLaughlin8of Texas, in an exhaustive series of studies begun as far back as 1885, undoubtedly establishes the clearest claim to the discovery of the causative agent, but in spite of his clear and concise description of the method of procedure employed, very few investigators have been able to verify the presence in dengue blood of the micrococcus which he found in such large numbers. Our lack of exact knowledge concerning the morbid anatomy of this infection