1. The Negri bodies, as the etiological agent in rabies, present two general types or phases in morphology, in growth, and in reproduction.
2. These two phases are constantly cyclic in their development and correspond (1) to a multiplicative, or schizogonous, and (2) to a reproductive, or sporogonous, life cycle.
3. By the detailed study of these forms and their succeeding stages we are inclined to believe that the Negri bodies are definite protozoan parasites, and from a study of their life history we are led to place them in the suborder of Cryptocysts, or Microsporidia, of the Sporozoa, and more definitely among the Oligosporogenea of the Glugeidae family, which forms produce but one pansporoblast.
With the recent advances in the growth of tissues outside the body, particularly the work of Carrel, Burrows, Harrison, Lewis and Lewis, and Rous upon the infectiousness of tumor extracts, with the results of Noguchi in cultivating pathogenic Treponema pallidum, important discoveries concerning the Negri bodies will undoubtedly be made in the near future.