The hygiene of transmissible diseases; their causation, modes of dissemination, and methods of prevention . from the red blood-corpus-cles that have been destroyed. In addition to the small and large amceboid and pigmentedforms that are regularly observed in the developmental cycleof the parasite, in tertian, quartan, and aestivo-autumnal fevers,other forms are encountered. The most conspicuous of these 1 The above description is condensed from Thayer and Hewetson, loc. 194 HYGIENE OF TJ^ANSMISSIBLE DISEASES. are the flagellated varieties and the crescents (Fig. 24).The former are seen
The hygiene of transmissible diseases; their causation, modes of dissemination, and methods of prevention . from the red blood-corpus-cles that have been destroyed. In addition to the small and large amceboid and pigmentedforms that are regularly observed in the developmental cycleof the parasite, in tertian, quartan, and aestivo-autumnal fevers,other forms are encountered. The most conspicuous of these 1 The above description is condensed from Thayer and Hewetson, loc. 194 HYGIENE OF TJ^ANSMISSIBLE DISEASES. are the flagellated varieties and the crescents (Fig. 24).The former are seen in one or all varieties of intermittentfever, usually at or about the period of the paroxysm; andin the aestivo-autumnal fever Thayer and Hewetson frequentlydetected them in the blood-specimens long after all febrilesymptoms had disappeared. They are easily recognized,consisting of a pale, pigmented body often as large as, some-times larger (according to circumstances) than a red corpus-cle, which is provided with one or more slender, thread-likeflagella that lash about in a very active manner. One or. Fig. 24.—Crescentic and flagellated forms of Plasmodium malariae: i, flagel-lated form of tertian fever; 2, flagellated form of quartan fever; 3, crescents, and4, flagellated form of gestivo-autumnal fever (after Thayer and Hewetson). more flagella may become detached and lead an independentexistence. The pigment-granules contained within the bodyare in active dancing motion, and an amoeboid movement ofthe body can usually be made out. For reasons too numer-ous to discuss here, the flagellated forms are regarded bymany to be degenerative forms of the parasite, while, on theother hand, others consider them to represent the organismin its highest stage of development. In his paper On the Hematozoon Infection of Birds, MacCallum describes an observation of fundamental impor-tance that he has made upon the developing parasites in theblood of crows. He has that in a partic
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Keywords: ., bookcentury1800, bookdecade1890, booksubject, booksubjectdiseases
