[Morphometric development of ossification in the chick leg from the 7th to the 17th day of incubation].

We attempted by ponderal means to define more precisely some parameters of the normal hen-egg incubation. We determined by double staining the appearance time of primary ossification centers in the limb skeleton, and demonstrated that there are appreciable chronological differences between the Hubbard and White Leghorn stains. It seems necessary to take them in consideration for teratological studies. Owing to length measurements, we established linear regressive equations, which are characteristic for each skeletal element of the limb, especially after the onset of ossification. Bones differentiate in length after that period, according to their proximo-distal position. By such a method, it is possible to determine the skeletal age of chick embryos from 7 to 17 days of incubation. This is important for the study of factors which could modify the skeletal development, and for evaluation of its modifications in importance and time of onset.