514
DYSENTERY
[CHAP.
Wenyon, and Walker, the distinctive features of the two species (see also Figs. 78, 79):
| Entamœba coli. | Entamœba histolytica |
| Size 15-25 μ. | (tetragena). Size 20-30 μ. |
| No well-marked distinction between ecto- and endoplasm; latter stains more deeply. | Ectoplasm distinct, much more refractile and more deeply staining than the finely granular endoplasm. |
| Rarely shows a vacuole. | Usually one or more non-contractile vacuoles. |
| Rarely contains erythrocytes, crystals, or bacteria, etc. | Often contains large numbers of erythrocytes, crystals, bacteria, etc. |
| Nucleus sub-central and almost always visible; stains deeply; shows a well-marked, rather thick, and very refractile nuclear membrane; contains nucleolus and large amount of chromatin. | Nucleus excentric, small, usually indistinct, stains feebly, contains little chromatin, and has no marked nuclear membrane. |
| Motility very sluggish. | Motility more marked and definite. |
| Multiplication in the intestine by binary fission. On fæces becoming hard, or outside the body, encystment and formation of eight amœbulæ which are set free when swallowed. | Multiplication in the intestine by fission.[1] On faeces becoming hard, or outside the body, encystment formation of four amœbulæ which develop when swallowed. |
The majority of authorities do not recognize a sexual cycle in either species.
While many observers, partly as the result of their own work, but principally it would appear in deference to Schaudinn's great authority, have accepted in the main these descriptions, there are others, notably Musgrave and Clegg, who declare, after careful work extending over several years and carried on in exceptionally favourable circumstances, that they fail to confirm Schaudinn's statements.
In the course of their work Musgrave and Clegg made many important discoveries having a bearing, not only on the etiology but also on the prophylaxis of this type of dysentery They claim to have shown that under certain conditions what apparently were non-pathogenic amœbas, collected from a
- ↑ Hartmann and Darling have pointed out that Schaudinn's description of reproduction by a process of budding was the result of observing degenerating forms of the amœba.
