. The elements of experimental embryology. Embryology, Experimental; Embryology. 228 THE MOSAIC STAGE OF DIFFERENTIATION some of the original presumptive limb-area does not give rise in normal development to limb, but merely to flank, skin, and muscle. Similarly, if the 4-day leg-bud be divided longitudinally, so as to separate preaxial and postaxial halves, the fragment usually forms only those digits which it would have produced if left in situ and either a tibia or a fibula. The femur rudiment regulates to a miniature whole in each portion. The limb-bud thus appears to be. Fig. Ill Self-dif
. The elements of experimental embryology. Embryology, Experimental; Embryology. 228 THE MOSAIC STAGE OF DIFFERENTIATION some of the original presumptive limb-area does not give rise in normal development to limb, but merely to flank, skin, and muscle. Similarly, if the 4-day leg-bud be divided longitudinally, so as to separate preaxial and postaxial halves, the fragment usually forms only those digits which it would have produced if left in situ and either a tibia or a fibula. The femur rudiment regulates to a miniature whole in each portion. The limb-bud thus appears to be. Fig. Ill Self-differentiation of the femur-head joint, without function. The femur shown in the section belonged to a limb from which all nerve supply was excluded. In spite of the fact that the limb never functioned at all, the cartilage cells and fibres of the femur-head show the normal configuration. (From Hamburger, Arch. Entwmech. cxiv, 1928.) a thorough-going mosaic of predetermined but slightly overlapping regions (fig. no). The recognition of the existence of organ-fields, regions possessing a general determination for the production of certain structures, and undergoing progressive regional specification of detail, constitutes one of the major advances made in the analytical study of development. The organ-fields resemble the whole organ-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Huxley, Julian, 1887-1975; De Beer, Gavin, Sir, 1899-1972. New York [Hafner Pub. Co. ]
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