Thirty-five infertile men were divided into two groups: those with normal spermograms (15 cases) and those with oligospennia (20 cases). Each semen sample was examined by its penetration into zona-free hamster ova and by an improved Coulter counter apparatus for measuring the volume of spermatozoal head. Both groups were further divided into two subgroups: those with normal (above 15%) and those with abnormal penetration assay (0-10%).The relationship between sperm modal size and sperm cell penetration into hamster ova in both groups-the oligospermic and the normospermic-was calculated and was found to be nonsignificant (correlation index: -0,154). It appears that the inability of some human sperm cells to penetrate the zona-free hamster ova cannot be attributed to the spermatozoal size.

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