Quain's elements of anatomy . Fig. 702.—Outlines op the anterior Fig. 702. EXTREMITIES OT HUMAN KMBRYOES AT DIFFERENT AGES. (, after His.) A, at four weeks ; B, at five weeks ;C, at seven weeks ; D, at nine or ten weeks. deeper substance of the distalsegment; second, in the occur-rence of an inflection betweenthe middle and proximal seg-ments, the hollow of which in thefore-limb looks forward, and inthe hind limb backwards withreference to the axis of the trunk ;and third, in the rapid progressof- the deeper textm^al differen-tiation which leads to the de-velopment of the several component
Quain's elements of anatomy . Fig. 702.—Outlines op the anterior Fig. 702. EXTREMITIES OT HUMAN KMBRYOES AT DIFFERENT AGES. (, after His.) A, at four weeks ; B, at five weeks ;C, at seven weeks ; D, at nine or ten weeks. deeper substance of the distalsegment; second, in the occur-rence of an inflection betweenthe middle and proximal seg-ments, the hollow of which in thefore-limb looks forward, and inthe hind limb backwards withreference to the axis of the trunk ;and third, in the rapid progressof- the deeper textm^al differen-tiation which leads to the de-velopment of the several components of the limbs, such as the skeletal,muscular, dermal, nervous and vascular rudimentary limbs consist at first entirely of a mass of nearly 3 F 2. 804 FHAMEWOEK OF THE BODY. uniform blastemic cells derived from the parietal mesoblast, coveredsuperficially by the cuticular epiblast, which always presents at itsextremity a peculiar pointed or conical cap of thickened epidermis. (Seefig. 703.) The development of the parts of the limb now referred to, both in itslarger features and in its histological characters, is usually somewhatmore in advance in the anterior than in the posterior extremities. Fig. ^sp
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
