The development of the human body; a manual of human embryology . ng eventuallyunited to the membrane bone; these cartilages are tobe regarded as secondary epiphysial cartilages. The upper part of the cartilage of the second branchialarch also lies within the tympanic cavity and ossifies toform the stapes, while the portion of the cartilage imme-diately ventral to this ossifies as the styloid process of thetemporal bone. The succeeding moiety of the cartilageundergoes degeneration to form the stylo-hyoid ligament,while its most ventral portion ossifies as the lesser cornu ofthe hyoid bone. The
The development of the human body; a manual of human embryology . ng eventuallyunited to the membrane bone; these cartilages are tobe regarded as secondary epiphysial cartilages. The upper part of the cartilage of the second branchialarch also lies within the tympanic cavity and ossifies toform the stapes, while the portion of the cartilage imme-diately ventral to this ossifies as the styloid process of thetemporal bone. The succeeding moiety of the cartilageundergoes degeneration to form the stylo-hyoid ligament,while its most ventral portion ossifies as the lesser cornu ofthe hyoid bone. The great variability which may be ob-served in the length of the styloid processes and of thelesser cornua of the hyoid depends upon the extent towhich the ossification of the original cartilage proceeds,the length of the stylo-hyoid ligaments being in inverseratio to the length of the processes or cornua. The greater THE BRANCHIAL ARCH SKELETON. 205 cornua of the hyoid are formed by the ossification of thecartilages of the third arch, and the body of the bone is. Fig. 106.—Diagram showing the Categories to which the Bonesof the Skull Belong. The unshaded bones are membrane bones, the shaded represent thechondrocranium, while the black represent the visceral archelements. AS, Alisphenoid; ExO, exoccipital; F, frontal; Hy, hyoid;IP, interparietal; M, malar; Mn, mandible; Mx, maxilla; NA, nasal;P, parietal; Pe, periotic; SO, supraoccipital; Sq, squamosal; St,styloid process; Th, thyreoid cartilage; Ty, tympanic. formed from a cartilaginous plate, the copula, which unitesthe ventral ends of the two arches concerned. 206 THE DEVELOPMENT OF THE HUMAN BODY. Finally the cartilages of the fourth and fifth arches earlyfuse together to form a plate of cartilage, and the two platesof opposite sides unite by their ventral edges to form thethyreoid cartilage of the larynx. The accompanying diagram (Fig. 106) shows the vari-ous structures derived from the branchial arch skeleton aswell as so
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
