. Analysis of development. Embryology; Embryology. 684 Regeneration the blastema and weaker at the base of the limb. This brief increase in level extends over the fifth and ninth days, after which there is a decrease, and no alkaline phospha- tase is demonstrable after the twelfth day. As is apparent in Figure 240, changes in the phosphatase level occur with or before the first histological criteria of differentiation. It is essentially a formation from mesen- chyme derived from fibroblast cells rich in alkaline phosphatase or by similar cells secured from dedifferentiation of muscle and carti
. Analysis of development. Embryology; Embryology. 684 Regeneration the blastema and weaker at the base of the limb. This brief increase in level extends over the fifth and ninth days, after which there is a decrease, and no alkaline phospha- tase is demonstrable after the twelfth day. As is apparent in Figure 240, changes in the phosphatase level occur with or before the first histological criteria of differentiation. It is essentially a formation from mesen- chyme derived from fibroblast cells rich in alkaline phosphatase or by similar cells secured from dedifferentiation of muscle and cartilage. The possibility of an epidermal contribu- tion to the blastema seems at present most unlikely on the basis of former histological. > '>? > Fig. 240. both in embryonic limb formation and in larval limb regeneration. The cells compos- ing the regeneration blastema react dis- tinctively to phosphatase stains. Fibroblast and dedifferentiating muscle appear to fur- nish the chief components contributing to the blastema, a finding in agreement with those of Butler (33), Thornton ('38a,b, '42) and Forsyth ('46). The contribution of the epidermis to the blastema, as advanced by Godlewski ('28) and Rose ('48), receives no support from the studies on phosphatase localization and level. The phosphatase in the epidermis appears after the preliminary phases of regeneration are complete and it is seldom that the epidermis elements merge with the blastema. The problem of blastema origin then stands at present on a fairly substantial accumulation of material which clearly supports the older histological observations. studies which show the non-participation of epidermal structures as well as the later studies of Thornton ('38a,b), Manner ('53), Heath ('53) and Karczmar and Berg ('51). The descriptions of careful observers cannot easily be thrown aside and the indirect evidence on mitotic loci and the abundance of embryonal fibroblasts, combined with chimaeric limb regeneration s
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Keywords: ., bookcentury1900, bookpublisherphiladelphi, booksubjectembryology
