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Table 6
Differential
Morphology of Protozoa Found in Stool Specimens of Humans: Flagellates-Cysts
| Species | Size (Length) | Shape | Number of Nuclei | Other Features |
| Trichomonas hominis | No cyst. | |||
| Chilomastix mesnili | 6-10 mm. Usual range, 8-9 mm. |
Lemon shaped with anterior hyaline knob. | 1. Not visible in unstained preparations. | Cytostome with supporting fibrils. Usually visible in stained preparations. |
| Giardia intestinalis | 8-19 mm. Usual range. 11-12 mm. |
Oval or ellipsoidal. | Usually 4. Not distinct in unstained preparations. Usually located at one end. | Fibrils or flagella longitudinally in unstained cysts. Deep staining fibers or fibrils may be seen lying laterally or obliquely across fibrils in lower part of cyst. Cytoplasm often retracts from a portion of cell wall. |
| Enteromonas hominis | 4-10 mm. Usual range, 6-8 mm. |
Elongated or oval. | 1-4, usually 2 lying at opposite ends of cyst. Not visible in unstained mounts. | Resembles E. nana cyst. Fibrils or flagella are usually not seen. |
| Retortamonas intestinalis | 4-9 mm. Usual range, 4-7 mm. |
Pear shaped or slightly lemon shaped. | 1. Not visible in unstained mounts. | Resembles Chilomastix cyst. Shadow outline of cytostome with supporting fibrils extends above nucleus. |
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