The Parasitology of Pyoi^rhcea alveolaris. 191 



varies greatly in motility, some forms being very actively motile, 

 whilst others are comparatively sluggish. It possesses a very 

 distinct ectoplasm, the endoplasm being very granular and showing 

 many food vacuoles, which may contain bacteria, red corpuscles, 

 nuclei of leucocytes, and other material. The nucleus is usually 

 invisible in the living organism, and the form contains no contrac- 

 tile vacuole. This amoeba when stained by the iron-hsematoxylin 

 method shows a well-deKned ring-shaped nucleus with chromatin 

 distributed at the periphery, and a small central karyosome 

 (PI. XVI, fig. 1). Chromatin blocks are also occasionally present. 

 Frequently in stained preparations, the amoebse are so full of red 

 cells as to obscure the nucleus. That the majority of these bodies 

 are red cells is proved by the fact that examination in the living 

 condition often shows many quite fresh normal red cells within 

 the cytoplasm, and these on staining by Geimsa, stain in a 

 perfectly normal manner quite differently from the nuclei of 

 leucocytes which the amoebae also ingest. There can be no doubt 

 that this amoebae corresponds to the Amceba huccalis, described by 

 Steinberg in 1862, and more fully examined by Prowazek in 

 1904, and named by him Entamceba huccalis. This is, however, 

 undoubtedly the same organism as that described in 1849 by Gros, 

 and named Amceba (/ingivalis, and the name Entamoeba gingivalis 

 should therefore be used. The smaller amoeba found is remarkably 

 uniform in size, measuring on the average from 15 /t to 20 /i. It 

 is usually actively motile, throwing out blunt lobose pseudopodia 

 in all directions, but occasionally it may be quite sluggish. The 

 nucleus in the living condition, as obtained direct from the mouth, 

 is generally invisible ; but if some material containing these amoebae 

 is placed on a cover-glass, and this is inverted on a plain 2 p.c. 

 agar jelly containing polychrome methylene-blue, the nucleus 

 stains a faint purplish blue. The nucleus of Entamceba gingivalis 

 treated in the same manner does not stain. Iron-haematoxylin pre- 

 parations show the nucleus to correspond with the free living Vahl- 

 kampfia type of amceba (PI. XVI, fig. 2), viz. a big central karyosome, 

 containing the whole of the chromatin. The amoeba shows food 

 vacuoles containing bacteria, nuclei of leucocytes, and, occasionally, 

 red corpuscles, but no contractile vacuole has ever been observed 

 in preparations direct from the mouth. This type of amoeba has 

 been observed with Entamceba gingivalis in about 65 p.c. of the 

 cases examined. 



From previous work on amoebae (^) we were led to endeavour 

 to cultivate the amoebae found in pyorrhoea. Three different 

 jellies were originally tried, viz. (1) a plain 2 p.c. agar jelly, 

 (2) ordinary nutrient agar jelly, and (3) a jelly which had already 

 been found to be extremely useful in obtaining bacteria-free 

 growths of amoebae, and stimulating them to divide rapidly. The 

 jelly has the following composition : — 2 p.c. agar jelly, 90 c.cm. ; 



