. Quain's Elements of anatomy. rnal surfaces bypreaxial and postaxial ridges, and the two external surfaces are separated by an externalridge, which descends from the dorsal extremity of the bone to the joint-socket. It ison this external ridge, (jlcnoid in the scapula and cotyloid in the ilium, that in each casethe long head of the great extensor muscle of the limb is attached. The primitive arrange-ment is modified in two ways, viz., 1st, by the outgrowth to a greater or less extent of theedges of the rod, thus giving rise to fossfe in the situation of the original surfaces, and 2nd,by the o
. Quain's Elements of anatomy. rnal surfaces bypreaxial and postaxial ridges, and the two external surfaces are separated by an externalridge, which descends from the dorsal extremity of the bone to the joint-socket. It ison this external ridge, (jlcnoid in the scapula and cotyloid in the ilium, that in each casethe long head of the great extensor muscle of the limb is attached. The primitive arrange-ment is modified in two ways, viz., 1st, by the outgrowth to a greater or less extent of theedges of the rod, thus giving rise to fossfe in the situation of the original surfaces, and 2nd,by the occurrence of a rotation in different directions in the two limbs, the scapula outwards. Fig. 165.—Diagram of an early human EMBRYO, SHOWING THE RUDIMENTARYLIMBS IN THEIR SECOND POSITION. (Allen Thomson.) r, preaxial or radial and iDollex border ofthe thoracic limb ; u, its postaxial or ulnarand little finger border ; t, preaxial ortibial and hallux border of the pelvic limb ;./, its postaxial or ribular and little the ilium inwards, in accordance with the rotation Avhich takes place during the course ofdevelopment in the free part of the limb. The primitive vertebral sui-face of the scapulabecomes the prescapular or supraspinous fossa, while in the ilium the corresponding surfaceis the sacral, which, being connected to the vertebral column, undergoes but little change inposition. The postscapular or infraspinous fossa of the scapula is accordingly represented bythe iliac fossa of the ilium, and the subscapular fossa by the gluteal surface. (See the tableof homologous parts below.) Bones of the limbs.—In making the comparison of the bones composing the limbs them-selves, it is necessary to revert to the simpler relations subsisting between the limbs and thetrunk or vertebral axis of the body in embryonic life. In the earliest stage the limbs may besaid to bud out from the side of the trunk as flatfish semilunar flaps, so that they present a
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectanatomy
