Plasmodium ovale Stephens 1922

In 1922 J. W. W. Stephens the morphological characters of the asexual forms of a malaria parasite which he had studied in the blood of a patient from East Africa were different from those of any usually accepted species, and he proposed to establish the parasite as a new species with the name Plasmodium ovale . In 1927, in collaboration with D. U. Owen, he confirmed and extended the description from the study of a case infected in Nigeria. In 1930 Warrington Yorke and D. U. Owen studied another case from Nigeria and, by utilising this patient's blood in the practice of malariatherapy, they were able to show that the peculiar morphological features of the asexual stages of the parasite remain constant when it is passed from person to person by direct blood inoculation.