. Human embryology and morphology. Embryology, Human; Morphology. THE LIMBS. 301 segment of the pelvic girdle becomes fixed to the costal processes • the corresponding part of the scapula remains free. In the typical reptilian shoulder girdle, as in the pelvic (Fig. 242), two elements are formed in the ventral part of the arch—a posterior part—the coracoid, corresponding to the ischium, and an anterior—the pre-coracoid, corresponding to the pubes. Both elements reach the ventral median line in which the presternum is developed. In Ornithorynehus the coracoid element is represented by two bones
. Human embryology and morphology. Embryology, Human; Morphology. THE LIMBS. 301 segment of the pelvic girdle becomes fixed to the costal processes • the corresponding part of the scapula remains free. In the typical reptilian shoulder girdle, as in the pelvic (Fig. 242), two elements are formed in the ventral part of the arch—a posterior part—the coracoid, corresponding to the ischium, and an anterior—the pre-coracoid, corresponding to the pubes. Both elements reach the ventral median line in which the presternum is developed. In Ornithorynehus the coracoid element is represented by two bones—the cora- coid and epi-coracoid. The coracoid helps to form the glenoid cavity at its dorsal extremity; its ventral articulates with the presternum. In man and all higher mammals, in which mobility of the fore limb is of advantage for speed and free move- ment, the coracoid element is much reduced. It forms merely a process on the scapula, which it joins in man about the 15th year. It still enters into the formation of the glenoid cavity, the articular part (supra-glenoid) having a separate centre of ossification which appears in the 12 th year. It is possible that the costo-coracoid ligament may be derived from the ventral part of the coracoid post. asp. manub. inter-clau. lig. (inter-clauicle) ^represent pre-or epi-coracoid ytnemb. clauicle (primitiveclau.) ,cartilage acrom. coraco-clav. ligs. coracoid glenoid right scap. fr. behind. Fig. 245.—The Parts in the Shoulder Girdle of a human foetus which correspond with those of Ornithorynehus. element—the part which articulates with the sternum in the duckbill. The pre-coracoid in the shoulder girdle of the lizard corresponds to the pubic element in the pelvis. The pre-coracoid, which, like all the primitive elements of the pelvic and shoulder. 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
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
