The classification of malarial parasites from a zoologic standpoint did not at first meet with decided success, inasmuch as they were placed by some observers in the class of the sporozoa, by others in that of rhizopods. Yet now, as the outcome of the establishment of a sexual and an asexual cycle, as in the cocci didae, the conclusion that they belong to the sporozoa, like similar parasites in the lower animals, has been established, and it seems to us that this classification will probably be the final one. Among those who adopted this classification before our present standpoint was reached may be mentioned Metschnikoff, Danilewsky, and Labbe. The last recommended the subclassification of sporozoa (gregarinidia, coccidia, myxosporidia, sarcosporidia) into two further divisions, namely hemosporidia and gymnosporidia, and placed the malarial parasites of man in this last subdivision. The principal characteristics of the gymnosporidia are, according to Labbe: Complete intraglobular cycle of life; ameboid structure, even in the adult stage; reproduction, either by gymnospores within the blood corpuscle, without the formation of a cystic membrane, or by simple intraglobular division. Malarial parasites of man would then be placed in the genus Haemamoeba.
Corresponding to the discordant views as to the nature of the malarial parasite, numerous scientific appellations have been proposed for it. We will mention some of them:
1. Oscillaria malarise (Laveran), later repudiated by the author himself.
2. Haematozoon malarise (Laveran).
3. Haematophyllum malarise (Metschnikoff).
4. Plasmodium malarise (Marchiafava and Celli).
5. Hsematomonas malarise (Osier).
Smalarise (quartan), vivax (tertian), prsecox (pigmented quotidian), immaculata (unpigmented quotidian). B. Laverania malarise (order of crescents, Grassi and Feletti). Of all these names, only one has been adopted, and that the least appropriate. This is the name plasmodium, bestowed by Marchiafava and Celli on the small non pigmented young ameboid forms of estivoautumnal fever. It is consequently contrary to the meaning of these investigators, when, for instance, a full grown organism or a crescent is designated a plasmodium. That this name was chosen inaptly, even for the small ameboid organisms to which it was originally applied, is conceded by the authors themselves.
Zoologists designate, by the name plasmodium, those organisms which originate from the running together of numerous amebse, each one of which preserves its nucleus. In a scientific sense, therefore, a plasmodium is a plasma mass containing many nuclei. This, as is well known, does not apply to the malarial parasite, containing, as it does, almost without exception, only one nucleus. Moreover, this name is not available, because we are dealing not with one species, but with many, every one of which requires a special name in order to make it definite. Some of the other designations were undoubtedly chosen both rationally and appropriately, and might, therefore, be preserved. Yet I avoid choosing one from among them, because I am of the opinion that with the complete understanding of the place in zoology occupied by the parasites, it will be the duty of the special scientists to agree on a final name.
Until then we will continue to use the general expression, "malarial parasite." As will be seen later on, this is easily employed, even in the explanation of details. The author is complimented by the fact that a considerable number of German and foreign investigators have adopted his nomenclature, which is a good sign of its practicability.