The development of the human body; a manual of human embryology . resented. Indeed, confirmation oftheir existence may be found in the fact that during thecartilaginous stage of the skull the anterior condyloid THE SKULL. 93 foramina are divided into three portions by two cartilag-inous partitions which separate the three roots of thehypoglossal nerve. Itseems certain from theevidence derived fromembryology and compar-ative anatomy that thehuman skull is composedof a primitive unseg-mental chondrocraniumplus four vertebrae, thelatter being added to andincorporated with theoccipital portion of
The development of the human body; a manual of human embryology . resented. Indeed, confirmation oftheir existence may be found in the fact that during thecartilaginous stage of the skull the anterior condyloid THE SKULL. 93 foramina are divided into three portions by two cartilag-inous partitions which separate the three roots of thehypoglossal nerve. Itseems certain from theevidence derived fromembryology and compar-ative anatomy that thehuman skull is composedof a primitive unseg-mental chondrocraniumplus four vertebrae, thelatter being added to andincorporated with theoccipital portion of thechondrocranium. Emphasis must belaid upon the fact thatthe cartilaginous portionof the skull forms onlythe base and lower por-tions of the sides of thecranium, its entire roof,as well as the face region,showing no indication ofcartilage, the mesen-chyme in these regionsbeing converted into fi-brous connective tissue,which, especially in thecranial region, assumesthe form of a dense mem-brane. But in addition to thechondrocranium and thevertebrse incorporated. Fig. 99.—Frontal Section throughthe Occipital and Upper Cervi-cal Regions of a Calf Embryo MM. ai and ai1, Intervertebral arteries; be1first cervical intervertebral platebo, suboccipital intervertebral platec-z, cervical nerves; ch, notocbordK, vertebral centrum; m1-3, occipi-tal myotomes; ro4-5, cervical myo-tomes; o1-3, roots of hypoglossalnerve; vj, jugular vein; x and xi,vagus and spinal accessory nerves.— (Froriep.) 194 THE DEVELOPMENT OF THE HUMAN BODY. with it, other cartilaginous elements enter into the com-position of the skull. The mesenchyme which occupiesthe axis of each branchial arch undergoes more orless complete chondrification, cartilaginous bars beingso formed, certain of which enter into very close rela-tions with the skull. It has been seen (p. 97) thateach half of the first arch gives rise to a maxillary processwhich grows forward and ventrally to form the anteriorboundary of the mouth, wh
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
