At the New Orleans meeting of the American Medical Association we presented before the Section on Pathology and Physiology the results of our work on the cultivation of the ordinary rat trypanosome,Trypanosoma lewisi. The paper itself has appeared since then in the VaughanFestschrift.1The results obtained mark a distinct advance in our knowledge of the animal parasites since this was the first time that a pathogenic protozoön was successfully cultivated and its relation to the disease demonstrated by inoculation of pure cultures. At that time we expressed the belief that the methods employed would probably be found to be applicable to other trypanosomes, and this view we have been able to confirm with reference to one of the most important organisms of this group, namely,Trypanosoma brucei, the cause of nagana or the tsetse-fly disease of South Africa. The nagana material necessary for