Development of the skeleton in mouse fetuses of both sexes between 14.5 and 18.5 days post coitum

Ossification during embryogenesis of female and male mouse fetuses between 14.5 and 18.5 days post coitum (d.p.c.) was investigated with two methods. The Alizarin-red based method allows differential staining of cartilage and bone tissue on whole animal, however standard histochemical methods allow detailed identification of cells involved in ossification process. There were minor differences in the time of occurrence of some ossification centers between male and female mouse fetuses in a period of 14.5 - 18.5 d.p.c. At 14.5 d.p.c. ossification of female but not male mandible was observed and at 18.5 d.p.c. histochemistry demonstrated ossification in the phalanges in male but not in female.