The Discovery of the Intestinal Protozoa of Man.

Abstract

THE following lines are written with a twofold object: first, to re-direct attention to the discovery of the intestinal protozoa of man; secondly, to correct a mistake-which has already had far too long a life-in the identificatio,n of the organisms discovered. At the present moment the intestinal protozoa of man are being much studied and discussed; but the fact that some of them were seen and described nearly two hundred and forty years ago is, if not altogether unknown, at least widely ignored. When it is added that the discovery, whenever mentioned, is almnost invariably misunderstood, and consequently cited in a wrong connexion, there seems justification for the belief that a correct account of the whole matter may not be without interest. It is generally allowed that the free-living protozoa were discovered by the great Dutch microscopist Antony van Leeuwenhoek (1632-1723), who recorded his observations in a famous letter addressed to the Royal Society in the year 16762 But it is not so generally recognized that the same acute observer also discovered the first parasitic protozoa, and recorded his observations a few years later. The organisms were discovered in his own stools, and his description of them is therefore I At a meeting of the Section held December 17, 1919. 2 The letter is dated 1676, but it records observations made in the previous year and was