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Table 5
Differential
Morphology of Protozoa Found in Stool Specimens of Humans: Flagellates-Trophozoites
| Species | Size (Length) | Shape | Motility | Number of Nuclei | Number of Flagella* | Other Features |
| Trichomonas hominis | 8-20 mm. Usual range. 11-12 mm. |
Pear shaped. | Nervous, jerky. | 1 Not visible in unstained mounts. |
3-5 anterior. 1 posterior. |
Undulating membrane extending length of body. |
| Chilomastix mesnili | 6-24 mm. Usual range, 10-15 mm. |
Pear shaped. | Stiff, rotary. | 1 Not visible in unstained mounts. |
3 anterior. 1 in cytosome. |
Prominent cytostome extending 1/3-1/2 length of body. Spiral groove across ventral surface. |
| Giardia intestinalis | 10-20
mm. Usual range, 12-15 mm. |
Pear shaped. | “Falling leaf.” | 2 Not visible in unstained mounts. |
4 lateral. 2 ventral. 2 caudal. |
Sucking disk occupying 1/2-3/4 of ventral surface. Median bodies lying horizontally or obliquely in lower part of body. |
| Enteromonas hominis | 4-10 mm. Usual range, 8-9 mm. |
Oval. | Jerky. | 1 Not visible in unstained mounts. |
3 anterior. 1 posterior. |
One side of body flattened. Posterior flagellum extends free posteriorly or laterally. |
| Retortamonas intestinalis | 4-9 mm. Usual range, 6-7 mm. |
Pear shaped or oval. | Jerky. | 1 Not visible in unstained mounts. |
1 anterior. 1 posterior. |
Prominent cytostome extending approximately 1/2 length of body. |
*Not a practical feature for identification of species in routine fecal examinations
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