Quain's elements of anatomy . vertebra ; it islargest opposite the fifth or sixthcervical vertebra, where it measuresfiom 13 to 14 mm, from side to lower or lumbar enlargementbegins at the tenth dorsal vertebra,is largest opposite the twelfth dorsal(11 —13 nun. across), and from thispoint becomes gradually smaller; itsantero-posterior diameter is more nearlyequal to the transverse than is the casein the cervical enlargement. Below exteejstal form. 263 the lumbar enlargement the cord tapers in the form of a cone {cotiusmeduUaris), from the apex of which the small filiform prolongation
Quain's elements of anatomy . vertebra ; it islargest opposite the fifth or sixthcervical vertebra, where it measuresfiom 13 to 14 mm, from side to lower or lumbar enlargementbegins at the tenth dorsal vertebra,is largest opposite the twelfth dorsal(11 —13 nun. across), and from thispoint becomes gradually smaller; itsantero-posterior diameter is more nearlyequal to the transverse than is the casein the cervical enlargement. Below exteejstal form. 263 the lumbar enlargement the cord tapers in the form of a cone {cotiusmeduUaris), from the apex of which the small filiform prolongation iscontinued downwards. The cervical and lumbar enlarg-ements tave an evident relation to the largesize of the nerves which supply the upper and lower limbs, and which are con-nected with those regions of the cord. At the commencement of its developmentin the embryo, the spinal cord is destitute of these enlarg-ements, which, in their fustappearance and subsequent progress, correspond with the growth of the Limbs. Fiff. Fig, 244.—Posterior view of the mebulla oblongata and of the spinal cord with: IIS COVERINGS AND THE ROOTS OF THE NERVES (Sappey). J The theca or dura-matral sheath has been opened by a median incision along the wholelength, and is stretched out to each side. On the left side, in the upper and middle parts(A and B), the posterior roots of the nerves have been removed so as to expose the liga-mentum denticulatum, 9, and the anterior roots, 13 ; and along the right side the pos-terior roots, 10, are shown arising from the postero-lateral groove, and passing out throughthe dura mater. The roman numbers indicate the different nerves in the cervical, dorsal,lumbar, and sacral regions respectively ; 11, posterior median fissure ; 12, ganglia onthe posterior roots ; 14, the united nerve beyond the ganglion ; 15, tapering lower endofthe spinal cord; 16, fikim terminale ; 17, cauda equina. The terminal filament (filmn terminale, central ligament) (, h, l)
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