<)6 AMOEBAE LIVING IN MAN 



specimens, of uniform size and closely packed together, so that the 

 nucleus appears as a very definite and even ring in optical section 

 (figs. 93, 94). The ring is of approximately the same thickness as m 

 E. coli, but is usually more uniform. The spherical karyosome (figs. 

 93, 94), which measures about 0*5-075 fM in diameter, is sometimes — but 

 not always — surrounded by a palei area, like the ** halo " in E. coli and 

 E. histolytica. The karyosome itself appears to consist entirely of 

 chromatin. According to Prowazek (1904) it consists of several separate 

 granules, but I have not seen such a structure in normal individuals, and 

 1 believe his statement is incorrect. In position the karyosome may be 

 either eccentric (fig. 93) or central (fig. 94). In this character the 

 organism appears to occupy an intermediate position between E. coli 

 and E. histolytica ; its karyosome being not so constantly eccentric as in 

 the former, nor so constantly central as in the latter. Between the 

 karyosome and the peripheral " ring " of chromatin there is a clear 

 space, which appears to me to be entirely free of chromatin or other 

 granules in normal well-stained specimens. In this respect E. gingivalis 

 thus resembles E. histolytica, and differs from E. coli. 



Smith and Barrett (1915) state that a "centriole" is sometimes 

 present in the kar^'^osome. Prowazek also believed that there is a 

 centriole — to judge from the statements of Hartmann (1913) — though 

 according to his earlier interpretation he regarded the whole karyosome 

 as a "nucleus" within the real nucleus (cf. Hartmann and Prowazek, 

 1907, p. 316). Smith and Barrett (1915, 1915 a) state that the nucleus 

 itself is more often central in position than in E. liistolytica. The exact 

 position occupied by the nucleus of an amoeba is, however, difficult to 

 define : and the " eccentric " nucleus of the Eiitamoebae is a character 

 upon which too much reliance should not be placed. 



The endoplasm of E. gingivalis, as already noted, usually contains 

 numerous food-vacuoles which enclose peculiar ingested bodies. These 

 are generally round or oval, and stain very intensely with nuclear stains ; 

 but if the stain is suitably extracted they are seen to be composed of 

 granules of variable size. In specimens deeply stained with iron- 

 haematoxylin they appear black and homogenous, and resemble the 

 ingested red corpuscles in E. histolytica. That they are not red 

 corpuscles, however, can easily be demonstrated by suitable staining 

 and by examination of the living animal. From their staining reactions 

 the bodies consist mainly of chromatin. According to Goodey and 

 Wellings (1916) they are the "nuclei of degenerated and disrupted 

 salivary corpuscles " occurring in the mouth. Goodrich and Moseley 

 (1916) say that they are the "nuclei of lymphocytes or other mononu- 

 clear leucocytes." But Smith and Barrett (1915) appear to believe that 

 the inclusions are partly leucocyte nuclei and partly red corpuscles. 

 They believe that red corpuscles are frequently ingested by E. gingivalis ; 

 but they say that these are soon haemolysed after ingestion, so that they 

 rapidly disappear. Goodey and Wellings (1916) deny that E. gingivalis 

 ever ingests red corpuscles or polymorphonuclear leucocytes, but 

 Goodrich and Moseley (1916) state that both of tliese " have been seen" 

 within the organisms. Prowazek (1904) merely stated that the food 

 consists partly of "leucocytes," but he did not specify the kind. 

 Nowlin (1917^) refers to the "solid masses" in the cytoplasm, but 

 never observed E. gingivalis ingesting red corpuscles or leucocytes. 

 This worker expresses the peculiar opinion that the organism "absorbs 



