A new malaria parasite of man

In the autumn of 1913 Major Kenrick, I. M. S., kindly sent me, from Pachmari, Central Provinces, India, a blood slide from a native child, containing numerous malaria parasites. On examining these, which I at first took to be malignant tertian parasites, the suspicion arose in my mind that there was something peculiar about their appearance. I happened just previously to have been studying a blood slide from Rhodesia, containing very numerous malignant tertian parasites. The peculiarity of the Indian parasite, as far as I could at first define it, was that it was an irregular parasite as compared with the regular, almost monotonous, contour of the “rings” of the malignant tertian parasite (Plasmodium falciparum ). I proceeded then to study the Indian parasite more carefully; and, after-daily observations for many weeks of it, and of control malignant tertian parasites from various sources, I came definitely to the conclusion that it was unlike any malignant tertian parasite that I had ever seen or that I could find figured in the text-books or journals. I also considered carefully the possibility of its being the simple tertian parasite, but to this point I shall return later. During this study, in order to fix my impressions, I drew 150 consecutive parasites from the Indian slide and the Rhodesian slide respectively, as the former appeared in the field of view of an ocular so restricted by placing a diaphragm in it that only half a dozen red cells were visible in the field at a time, thus effectively preventing any selection on my part. I reproduce as pen-and-ink drawings 35 of each series taken at random, as they show very well in a general way the different aspect of the two parasites. For the same purpose I also drew a number of young simple tertian parasites. I now proceed to define as far as possible in detail the peculiarities of this parasite.