The appearance of quartana duplex or triplex is conditional on the presence in the blood of the patient of two or three groups of Plasmodia differing in their development by twenty-four hours.
The chief distinctive characters of the quartan parasite are: (1) The erythrocyte is unchanged in size; (2) the rings are compact and show pigment early; in the larger forms the chromatin is dense and relatively plentiful; (3) the pigment, which is relatively well-marked, may be arranged at the periphery.
Laverania malariæ, Grassi and Feletti, 1890 = Plasmodium falciparum, Welch, 1897.
Syn.: Plasmodium malariæ var. quotidianæ, Celli et Sanf., 1891; Hæmamœba malariæ præcox, Gr. et Fel., 1892 (nec H. præcox, Gr. et Fel., 1890); Hæmamœba laverani, Labbé, 1894; Hæmatozoön falciparum, Welch, 1897; Hæmosporidium undecimanæ and H. sedecimanæ and H. vigesimo-tertianæ, Lewkowitz, 1897; Hæmamœba malariæ parva, Lav., 1900; Plasmodium præcox, Dofl., 1901; Plasmodium immaculatum, Schaud., 1902; Plasmodium falciparum, Blanch., 1905.
The names most commonly used for the parasite of malignant tertian malaria are Plasmodium falciparum and Laverania malariæ.
The summer and autumn fever (febris æstivo-autumnalis), also called malignant tertian or sub-tertian, is caused by a malarial parasite which is distinguished by the small size of its schizont, while the gametocytes are crescentic (figs. [81], 88).
Most authors identify this kind of fever or the parasites which cause it (Laverania malariæ) with the pernicious malaria of the tropics. Ziemann, however, repeatedly has drawn attention to certain small but definite differences between the usual malignant tertian or pernicious parasites which occur in the tropics and the tropical parasites of some malarial districts, particularly of West Africa, and insists that at least two varieties or sub-species occur. Other investigators distinguish from this or these forms a quotidian parasite. On the other hand, the assertion is made that there are no specific differences, but that the malignant or pernicious tertian parasite which normally needs forty-eight hours for its development in the blood of man, can also develop in twenty-four hours. The establishment of the duration of the development is a matter of especial difficulty, because the stages of schizogony are far less numerous in the peripheral blood than in that of the internal organs. It is also stated that the tropical parasite very seldom forms crescentic but rather rounded gametocytes. According to such an observation the organism would belong to Plasmodium and not to Laverania. The question whether the tropical fevers are caused by two different parasites does not seem to be definitely settled.
The young trophozoite of the malignant, pernicious tertian, or sub-tertian parasite (fig. 87) are but slightly active and are very small, even after the formation of the comparatively large food vacuole, which makes the body appear annular (“signet ring” stage). Often two and even more parasites are found in one blood corpuscle.