Davaine found flagellates in the dejecta of cholera patients. They had pear-shaped bodies, lengthening to a point posteriorly. Their length was from 10 µ to 12 µ, and a flagellum about twice as long as the body projected from one extremity (fig. 21). A nucleus was hardly recognizable. Occasionally a somewhat long structure (cytostome?) appeared at the anterior extremity. The animals moved with remarkable activity. They also attached themselves by means of their posterior extremities and swung about around the point of attachment. Davaine found a smaller variety, only about 8 µ long, in the dejecta of a typhoid patient (fig. 21, b).
Fig. 21.—Cercomonas hominis, Dav. a, larger, b, smaller variety. Enlarged. (After Davaine.)
Fig. 22.—Cercomonas hominis, Dav. From an Echinococcus cyst. (After Lambl.)
The Flagellata observed by Ekeckrantz (1869) in the intestine of man belong to this form—at least to the larger variety—and Tham (1870) reported fresh cases soon after. Lambl’s publication of 1875, which was written in Russian, and became known through Leuckart’s work on parasites, also alludes to apparently typical Cercomonads, which, however, were discovered, not in the intestine, but in an Echinococcus cyst in the liver (fig. 22). The elliptical, fusiform, rarely pear-shaped or cylindrical bodies of the parasites measured 5 µ to 14 µ in length, and were provided with a flagellum at one end, while the other extremity usually terminated in a long point. An oral aperture occurred at the base of the flagellum, and there were one or two vacuoles near the posterior extremity. Longitudinal division was also observed (fig. 22).
As already mentioned, this form, which Lambl termed Cercomonas intestinalis, differs considerably from the form found by the same author in 1859, which received the same designation (cf. Lamblia intestinalis, p. [60]), but it corresponds with Cercomonas hominis, Davaine. The latter, as well as C. intestinalis, Lambl, 1875, is usually classed with the Trichomonads, but, as has already been remarked (cf. Trichomonas intestinalis, p. [54]), this cannot be considered correct, as only one flagellum is present.