During the course of a survey on the intestinal protozoan infections among 362 children in St. Louis by one of us1 (Dr. Tsuchiya), three cases of infection with Hymenolepis nana were incidentally encountered. Two of the patients came from an orphanage; the other, from a hospital. Though the infection is known to be common in crowded institutions, as exemplified by the report of Frey,2 who found this infection present in 86 among 270 children (32 per cent) in an orphanage in Texas, the number of cases reported in the country at large has been low as compared with the studies made elsewhere. Goldman3 has systematically reviewed most of the literature up to 1920. He reported, in addition, seven cases in a colored family, which were the first instances described in St. Louis. Spindler4 recently reported that of 2,152 examinations of stools made during a survey in