252 FAMILY: AMCEBID^ 



vacuoles. Examined in iodine solution, the details are more readily seen, 

 for the nuclei of the cysts of E. histolytica are not easily distinguished in 

 saline solution. Very active amoebae with very marked ectoplasm and 

 pseudopodia being formed entirely of ectoplasm, are most probably 

 E. histolytica. If the amoebae are about 10 to 15 microns in diameter, 

 then diagnosis is difficult, and a careful search in saline and iodine solution 

 must be made for cysts of E. coli, E. histolytica, or I. butschlii. The 

 last is distinguished by its deeply staining iodophilic body and single 

 nucleus; the others by the number of nuclei and presence or absence of 

 chromatoid bodies. If no cysts can be found, it will be necessary to 

 make stained films, when /. butschlii can be recognized by its large 

 central karyosome. If its nucleus has a small karyosome and chromatin 

 granules on the membrane, an amoeba may be E. histolytica or E. coli. 

 Attention to details of the nuclear structure, as described above, may 

 assist in diagnosis, but it must be admitted that there is difficulty in 

 distinguishing the precystic forms of these amoebae. 



If precystic amoebae occur in any specimen, then it is very unusual for 

 cysts not to be present also, and if they are not found at the first examina- 

 tion, later examinations will almost certainly reveal them. 



If the amoebae are quite small and vary in size from 5 to 10 microns, 

 or a little over this, they may be free forms of E. nana, precystic forms of 

 small races of E. histolytica, I. biitschlii, or D. fragilis. Here, again, 

 the discovery of cysts will enable a diagnosis of the first three to be 

 readily made. If cysts cannot be found, then films must be stained. 

 The small forms of E. histolytica will show their characteristic nuclei, and 



D. fragilis the two nuclei characteristic of this amoeba. Amoebae 

 with a single nucleus, showing a large, irregularly-shaped karyosome, are 

 almost certainly E. nana, though it is just possible they may be difficult 

 to distinguish from /. biitschlii, which, however, is rarely seen in 

 the unencysted condition. If /. biitschlii is present, its cysts will almost 

 certainly be found and recognized in iodine solution. The cysts of 



E. nana are typically of an ovoid shape, while the small cysts of E. histo- 

 lytica are usually spherical or nearly so. The small cysts of E. histolytica 

 often show chromatoid bodies, and the details of the cysts and those of 

 E. nana should be quite clear in properly stained films. 



It must be remembered that in the great majority of cases a diagnosis 

 can be arrived at by the careful examination of thin saline and iodine 

 preparations, and that stained films are only necessary in exceptional cases 

 or for confirmatory purposes. 



The presence in large amoebae of food vacuoles containing bacteria, 

 yeasts, or other objects, amongst which may be cysts of the intestinal 

 Protozoa, such as those of E. histolytica, Giardia intestinalis, Isospora 



