The chief distinctive characteristics of the simple tertian parasite, as seen in infected blood, are:—(1) The infected red-cell is usually enlarged; (2) the presence of fine red granules known as Schüffner’s dots in the red blood corpuscles, after Romanowsky staining; (3) the fragile appearance of the parasite compared with other species. Large forms are pigmented, irregular and “flimsy-looking,” sometimes appearing to consist of separate parts. Irregularity of contour is common.
Ahmed Emin[203] (1914) has described a small variety of P. vivax.
Plasmodium malariæ, Laveran.
Syn.: Oscillaria malariæ, Laveran, p.p., 1883; Hæmamœba malariæ, Gr. et Fel., 1890; Plasmodium malariæ var. quartanæ, Celli et Sanfel., 1891; Hæmamœba laverani var. quartana, Labbé, 1894; Hæmosporidium quartanæ, Lewkowitz, 1897; Plasmodium malariæ quartanum, Labbé, 1899; Plasmodium golgii, Sambon, 1902; Laverania malariæ, Jancso, 1905 nec Grassi et Fel. 1890; Hæmomœba malariæ var. quartanæ; Lav., 1901.
Plasmodium malariæ is the parasite of quartan malaria (fig. 86). The trophozoites of the quartan parasite differ from the corresponding stages of the tertian parasite in that their motility is less and soon ceases. They differ also in their slower growth, by the early disappearance of the food vacuole, by the more marked formation of the dark brown pigment, and by the fact that the red blood corpuscles attacked are not altered either in colour or size.
Fig. 86.—Development of the quartan parasite in the red corpuscles of man—asexual stages. (After Manson.)
When the parasites have grown almost to the size of the erythrocytes schizogony occurs. The pigment granules arrange themselves in lines radiating towards the centre and the merozoites are also radially disposed in groups of 6, 8, 10 or even 12, but are often arranged less regularly. The whole development, growth and schizogony, occupies seventy-two hours.