388 Encystment of Dysentery Ameb

I t has been stated in the literature that the vegetative form of the dysentery ameba dies within a few hours outside of its host and forms no cyst. In a study made in 1917, the author has observed, however, that the large vegetative ameba of dysentery is transformed into a smaller vegetative form, and that occasionally it develops in vitro a tetranuclear cyst. Proliferation takes place in fecal material containing blood and mucus. On the basis of these experiments we may conclude that the process of encystment of the dysentery ameba and change from the vegetative form proceed in nature in a manner similar to that observed in specimens taken from the host. The latter fact is most significant in the prophylaxis of amebic dysentery.