Attempts to Produce Encystment in Chilomastix.

Abstract

The life histories of mammalian intestinal flagellates, particularly with reference to the process of encystment, have been investigated with much less satisfactory results than have those of the intestinal amoebae. Practically nothing is known regarding the conditions producing encystment or excystment in these forms. The results here reported are largely negative, but it seems worth while to summarize them briefly since they show what conditions are incapable of producing encystment in vitro, and since, furthermore, this phase of the investigation is being abandoned.

Da Cunha and Muniz 1 are the only workers to report encystment of Chilomastix mesnili in culture; their successful results were obtained with ordinary blood agar and with N.N.N. medium, on which the flagellates encysted in great numbers after being grown for 48 hours at 37°C. Experimental production of encystment in C. intestinalis from the guinea pig has been reported by Hegner. 2 Washed cysts from guinea pigs were fed young chicks and apparently hatched in the digestive tract of the latter, since motile forms were discharged in cecal droppings 6 days later. Four days after this, cysts as well as trophozoites were abundant in the cecal droppings, but by the fourteenth day the infection had disappeared. The chick, in this instance, served as a living culture tube.

In a series of experiments running over several years, Chilomastix mesnili was cultivated successfully in a number of standard culture media, such as ovo-mucoid, Ringer-egg (with and without albumen), Locke-egg (with and without albumen), and Locke-egg-serum. In cultures continued over several months, there was no evidence of anything approaching a life cycle, such as any rhythmic variation in the division-rate; and no cysts were ever found. On Locke-egg-albumen, the flagellates appear able to grow and multiply indefinitely without producing cysts.