The Polymastigina contains flagellates with three to eight flagella. Some of the Flagellata parasitic in man belong to the Polymastigina, and to two or three genera that are easily distinguishable.
Genus. Trichomonas, Donné, 1837.
The body is generally pyriform, the anterior part usually rounded, the posterior part pointed. There are at the anterior extremity three (? four) equally long flagella that are sometimes matted together. A blepharoplast (kinetic nucleus) and basal granule are present, together with a supporting structure known as an axial filament or axostyle. In addition there is an undulating membrane, bordered by a trailing flagellum, that commences at the anterior extremity and proceeds obliquely backwards. The nucleus, which is vesicular, is situated near the anterior extremity, and behind it are one or more vacuoles, none of which seems to be contractile. These flagellates are parasitic in vertebrate animals, and live chiefly in the intestine.
Trichomonas vaginalis, Donné.
The form of the body is very variable, and is elongate, fusiform or pear-shaped, also amœboid. The length varies between 15 µ and 25 µ, and the breadth between 7 µ and 12 µ. The posterior extremity is drawn out to a point and is about half the length of the remainder of the body. The cuticle is very thin and the body substance finely granular. At the anterior extremity there are three—some say four[36]—flagella of equal length which are frequently united together, at least at the base, and are easily detached.
There is an undulating membrane (fig. [16]) which runs spirally across the body, arising from the place of insertion of the flagella, and terminating at the base of the caudal process. A cytostome seldom is recognizable in fresh specimens, but is apparently present. The nucleus is vesicular, elliptical and situated near the anterior extremity.[37]
Multiplication takes place by division (Marchand). Encysted forms are almost unknown.
Trichomonas vaginalis lives in the vaginal mucus of women of various ages, not in normal mucus, but in mucus of acid reaction. It is found in menstruating females as well as in females who have passed the menopause. It occurs in pregnant and non-pregnant women, even in very young girls, provided always that they have a vaginal catarrh with acid reaction of the secretion. Should the acid reaction change, as, for instance, during menstruation, the parasites disappear, as they do likewise on injection of any alkaline fluid into the vagina. A low temperature (below +15° C.) is also fatal to the parasites. These flagellates can pass from the vagina through the urethra into the bladder, and produce severe catarrh, and are not easily removed.
