. Cunningham's Text-book of anatomy. Anatomy. Myotome -Septum Body of vertebra Hypochordal bow Rib Notochord A B Fig. 117.—The Development of the Membranous Basis of a Vertebra (after Keith). A, in transverse section. B, in horizontal section, showing the relation of the vertebrae to the primitive segments. arch, the extremities of which usually unite dorsally about the fourth month of foetal life; if from defective development this union should fail to occur a deformity known as spina bifida is the result. From the cartilaginous vertebral arch, so formed, arise the chondrified rudiments of th
. Cunningham's Text-book of anatomy. Anatomy. Myotome -Septum Body of vertebra Hypochordal bow Rib Notochord A B Fig. 117.—The Development of the Membranous Basis of a Vertebra (after Keith). A, in transverse section. B, in horizontal section, showing the relation of the vertebrae to the primitive segments. arch, the extremities of which usually unite dorsally about the fourth month of foetal life; if from defective development this union should fail to occur a deformity known as spina bifida is the result. From the cartilaginous vertebral arch, so formed, arise the chondrified rudiments of the spinous, transverse, and articular processes. The chondrification of the vertebral arch is variously described as being in- dependent of the body or an extension from it; in any case, union between it and the body is rapidly effected. The scleratogenous tissue between the cartilaginous vertebral arches which does not undergo chondrification persists as the ligaments uniting the vertebral laminaj. As regards the so-called hypochordal bow, for the most part it disappears. By some&it is regarded as being represented by a fibrous strand in the inter- vertebral fibro-cartilage in front of the vertebra to which it belongs. It is, however, noteworthy that in the case of the atlas vertebra there is an exception to this arrangement; for here the hypochordal bow chondrifies and subsequently by ossification forms the anterior arch of that bone—an arch which lies ventral to, and embraces the dens of the epistropheus ( p. 91). It is only in the thoracic region that the ribs, developed as stated above by the chondrification of the intersegmental septa, attain their full dimensions. In the cervical lumbar, and sacral regions they exist only in a rudimentary or modified form as has been described elsewhere. In the construction of the chest wall the ribs are supported ventrally by the sternum, as to the development of which there is some difference of opinion. Kuge has described t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
