071 Certain Parasites of the Mouth in Cases of Pyorrhoea. 519 



•amoebse, but in ten or twelve cats with the disease in advanced 

 stages we have only found them once. In both these animals the 

 amceb?e, so far as we have been able to study them, are indistin- 

 guishable from the human one, Entamoeba ginrjiudis. 



Structure of Entamceba gingivalis, Gros. 



There is great variation in size among the ordinary vegetative 

 forms. Sometimes chiefly small ones, measuring up to 10 or 15 yu, 

 in diameter, are found ; at other times there will be numbers of 

 large ones full of the characteristic inclusions and having diameters 

 of 20-30 /Lt. However, with a little trouble all intermediate sizes 

 may generally be found. At the ordinary room temperature 

 movement is somewhat sluggish, consisting in the extrusion of 

 lobose pseudopodia in various directions without any actual change 

 of place. On warming, the amoeb?e become very active and some- 

 times move rapidly across the field of the Microscope, and may 

 extend themselves to 100 /i or more in length. The pseudopodia 

 consist almost entirely of the refringent, slightly greenish ectosarc 

 (figs. 9, 10, 12 and 13). There is no contractile vacuole, but 

 the endosarc contains usually many food vacuoles. In small 

 specimens the contained food is often bacteria, but sometimes one 

 or two of the large inclusions, so typical of the larger amoebte, may 

 be distin<Tuished. There has been much discussion as to the nature 

 of these inclusions, and they have been described as such mysterious 

 things as " something of Protozoan nature " — Craig (rj) — or " bodies 

 only present in inflamed tissue." They are large, often 4-6 yu, in 

 diameter, refringent in the living, and stain readily with neutral 

 red, Ehrlich's haimatoxylin, and methyl-green. That is to say, 

 they do not behave as the red blood corpuscles ingested by 

 Entamoeba histolytica, but seem to be composed of nuclear matter. 

 In fact we consider that they are the nuclei of lymphocytes or 

 other mononuclear leucocytes. In this connexion it is interesting 

 to note that Mendel {10) has found 9 p.c. to 13 p.c. of the leucocytes 

 in the gingival space to be mononuclears. On ingestion the small 

 amount of cytoplasm would be rapidly digested, leaving the more 

 indigestible nuclei in food vacuoles of the living amceba for a long 

 time. Occasionally the branching nucleus of a polymorphonuclear 

 leucocyte has been seen, also on one or two occasions a red blood 

 corpuscle ; but these are very rare. Though living amoebse have 

 been kept under observation for long periods (they will live in saliva 

 or Ringer's solution in vitro for eight or nine hours) we have not 

 succeeded in seeing any large body actually ingested. An amoeba 

 has been seen to flow round a mononuclear leucocyte for a long 

 time witliout finally accomplishing its ingestion. When feeding 

 on bacteria amcebw have been observed on several occasions to 

 flatten themselves out and extrude numerous fine branching 



