An introduction to the osteology of the Mammalia : being the substance of the course of lectures delivered at the Royal college of surgeons of England in 1870 / By William Henry Flower.

Flower, William Henry, 1831-1899.

Date:: 1870

Credit: An introduction to the osteology of the Mammalia : being the substance of the course of lectures delivered at the Royal college of surgeons of England in 1870 / By William Henry Flower. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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$placed rather lower (Fig. 4, d), and which projects more or less backwards, and is generally rather slender or styliform, is called aiiapophysis. These, with the zygapophyses before mentioned, sometimes called oblique processes., but which are rather articular surfaces than true processes, are all the processes commonly met with on any Mammalian vertebra. Development of the VertebrcB.—The first indication of the formation of a vertebral column in the embryo, is the appearance of a longitudinal primitive dorsal groove in the germinal membrane, the edges of which {lamincs dorsales) rise up and meet above, so as to convert the groove into a canal. From the tissue lining this canal (uppermost layer of the germinal membrane) the brain and spinal cord are developed, and in its walls are formed anteriorly the cranium, and posteriorly the vertebral column ; the canal itself be- coming the cerebral cavity and the neural canal of the spine. In the floor of this canal, formed by a horizontal lamina which separates it from another and larger, ventral or h^mal canal (formed by the approximation in the middle line below of the lamincz ventrales), a slender rod of peculiar structure is developed. This is the notochord or chorda dorsalis, around which the bodies of the future vertebrae are developed. In the Mammalia it almost com- pletely disappears at a very early period, traces onlyremaining in the axis of the intervertebral substance, though in many of the inferior Vertebrata it is persistent as a continuous rod for a longer period, and sometimes permanently. The formation of the arches of the vertebrae in the lamince dorsales is preceded by the appearance of dark- looking cellular masses called proto-vei-tebrcz or somatomes, corresponding in number, though not exactly in situation, to$