Article révisé par les pairs
Résumé : After a re-examination of the macroscopical aspects of the development of the skeleton of the front leg in mouse embryos aged 12-18 days, several microscopical aspects of these changes have been studied in serial sections of the 11-16 day limb buds by histological, histochemical and autoradiographic methods after the incorporation of S35 sulfate. At the tissular level, whatever region is considered, the techniques used have made it possible to distinguish four successive stages in the progress of skeletogenesis: (1) the primary individualisation of the undifferentiated blastemas; (2) the start of chondrogenesis, immediately followed by the individualisation of the pre-articular interzones; (3) a stage of active chondrification emerging in parallel with the growth and modeling of the young cartilages; and (4) the start of the processes of primary ossification. When studied from stage to stage at the level of the various segmental areas, the changes progress in relation to a proximo-distal gradient on which a caudo-cephalic gradient is secondarily superimposed, being particularly evident at the autopodal level. The primordial constituents of the scapular girdle and the proximal region of the basipod sometimes combine their chondrogenesis with an obvious retardation in relation to that of more distant areas. A detailed analysis of the changes which occur in the basipodal region has finally made it possible to specify and correct the previous concepts in regard to the orgin of the various components of the wrist.