. On the anatomy of vertebrates [electronic resource] . rsal myelonal columns. § 56. Nerves of Reptiles.— The olfactory nerves are continuedin Reptiles, for a greater or less extent, from the rhinencephalon,figs. 188, 191, to the olfactory sacs; the white and grey tractsbeneath the prosencephalon, fig. 190, P, described as roots of thisnerve, belong to the rhinencephalic crura: the true olfactorynerves are less distinct from their centres than in other Ver-tebrates. In the Python, fig. 188, the nerves, \s of equaldiameter with their centres, gradually expand, by resolution oftheir fibres, as t
. On the anatomy of vertebrates [electronic resource] . rsal myelonal columns. § 56. Nerves of Reptiles.— The olfactory nerves are continuedin Reptiles, for a greater or less extent, from the rhinencephalon,figs. 188, 191, to the olfactory sacs; the white and grey tractsbeneath the prosencephalon, fig. 190, P, described as roots of thisnerve, belong to the rhinencephalic crura: the true olfactorynerves are less distinct from their centres than in other Ver-tebrates. In the Python, fig. 188, the nerves, \s of equaldiameter with their centres, gradually expand, by resolution oftheir fibres, as they approach the olfactory sacs, ib. d, and arejoined by part of the first division of the i fifth. The olfactory 310 ANATOMY OF VERTEBRATES. nerves progressively increase in length in the Turtle, Iguana, andCrocodile. The distribution of their fibres upon the vascularpituitary membrane, supported by the turbinal cartilage, is welldisplayed in a Hunterian preparation of the The optic nerves, corresponding in size with that of the eyes, 206. Cerebral, anterior spinal, and sympathetic nerves, Python, liv. are smallest in the fish-like Batrachians. They arise from theoptic lobes, fig. 192, o, thalami, and optic tracts, ib. d, and blend,by a few decussating lamina?, into a chiasma, ib. b, before diverg-ing to the visual organ: their course is shown, in the Python, at2, fig. 188. The position of the 6third or oculo-motor nerve is 1 xx. vol. iii. p. 89, nos. 1532, 1533. NERVES OF REPTILES. 311 shown at 3, fig. 188. The course of the fourth to the upperoblique muscle is shown at 4, fig. 188. This nerve does notexist, separately, in the fish-like Batrachians. The fifth or trigeminal nerve shows its double (ganglionic andnon-ganglionic) origins in all Reptiles, and its threefold primarydivision very distinctly, in all above the Perennibranchiates. Inthe Serpent the first division is shown at 5, fig. 188, extendingforward beneath the (fourth nerve and upper oblique muscle,and
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