[Proliferation and differentiation of isolated cells and symplasts of the skeletal muscle tissue of chick embryos].

By means of the radioautography, morphometry and alkaline dissociation methods musculus tibialis anterior has been studied in 30 chick embryos and chickens. The muscle fibers are variable in their diameter and length, number of nuclei 3H-thymidine-labelled including. The greatest variability of the structures is noted in 11-14-day-old embryos. Three classes of myotubes (MT) and symplasts are described. The primary MT are evidently the source of cellular elements, that form new cellular-symplastic structures (muscular-proliferative units) that develop, for some time, in a close connection with the primary MT. Between the extreme morphological variants of structure of the muscular elements, there is a transitional form. All the forms of the myosymplasts and MT reflect various stages of differentiation of the myogenic elements; this results in formation of the cellular-symplastic system--muscle fiber.