The object of the experiments described in this paper was to determine whether Plasmodium falciparum underwent an exo-erythrocytic development in the liver. They were undertaken independently of SHORTT and his associates, whose successful results were reported while the present work was in progress.

Fourteen paretic patients were inoculated with sporozoites from infected mosquitoes, by bite, by intravenous injection or by both methods combined, over a period of 2 to 6 days. The species used were in most cases Anopheles albimanus, but in some A. quadrimaculatus. The sporozoite material inoculated was obtained from numbers of mosquitoes varying from 116 to 9, 919. The results of the inoculations were assessed by microscopical examination of fixed and stained sections of portions of the liver removed with the aid of a peritoneoscopo (12 cases) and by laparotomy (2), from 2 to 8 days after inoculation. Positive results were obtained only in one patient, who received the heaviest dose of sporozoites, whereas in the 13 others no parasites could be detected. This patient had been inoculated 4 days in succession by a total of 8, 510 mosquito bites and 1, 403 salivary glands. In samples of the liver obtained by laparotomy 3 to 6 days after inoculation, 125 parasites representing exo-erythrocytic stages were found within the parenchyma cells. They were similar to those described by SHOETT et al., and are depicted in one coloured plate and in photomicrographs. CA Hoare.