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On the Structure, Division, and Systematic Position of Trichomonas vaginalis Donné, with a Note on its Methods of Feeding


1. Trichomonas vaginalis has been cultivated on various media and a simple method of maintaining cultures on Boeck and Drbohlav's egg-Ringer-albumen medium is described.

2. The feeding methods of the flagellates in culture have been studied and some evidence of extracellular digestion is recorded.

3. When cultivated on media deficient in carbohydrate, T. vaginalis is reduced to the dimensions of T. hominis, but when adequately fed it maintains its distinctively larger size. Out of forty-eight strains of T. vaginalis, only two developed in culture the long undulating membrane and free posterior flagellum typical of T. hominis in nature.

4. The structure of T. vaginalis has been reinvestigated. (i) It differs constantly and significantly from the intestinal trichomonads of man in size, nuclear organization, and the form of the axostyle and basal fibre, (ii) It also differs from T. hominis in the characters of its parabasal apparatus and cytoplasmic inclusions, and, in nature, in the length of its undulating membrane and in lacking a free posterior flagellum, but for reasons discussed in the text these points are at present considered less reliable in diagnosis than those given under 4 (i).

5. It is concluded that T. vaginalis is a species distinct from all other human trichomonads.

6. The method of division has been described. In general, it follows the same course as T. hominis, but separation of the old, and growth of the new, cytoplasmic structures occurs somewhat later in T. vaginalis, and the old axostyle is retained throughout division. There are five chromosomes, formed during prophase from aggregations of extra-karyosomatic granules.