. A text-book of embryology for students of medicine [electronic resource]. Embryology; Embryology. THE INTERNAL EAR. 347 pear-shaped owing to the protrusion of its dorsal wall. This dorsal projection, the recessus vestibuli or labyrinthi (Fig. 166, G), lengthens out into a slender tube, the ductus endo- lymphaticus (Fig. 168), the slightly dilated end of which, the saccus endolymphaticus, is found in the adult occupying the aqueductus vestibuli of the temporal bone. B c. Fig. 167.—Development of the membranous labyrinth of the human ear (W. His, Jr.): A, left labyrinth of embryo of about four
. A text-book of embryology for students of medicine [electronic resource]. Embryology; Embryology. THE INTERNAL EAR. 347 pear-shaped owing to the protrusion of its dorsal wall. This dorsal projection, the recessus vestibuli or labyrinthi (Fig. 166, G), lengthens out into a slender tube, the ductus endo- lymphaticus (Fig. 168), the slightly dilated end of which, the saccus endolymphaticus, is found in the adult occupying the aqueductus vestibuli of the temporal bone. B c. Fig. 167.—Development of the membranous labyrinth of the human ear (W. His, Jr.): A, left labyrinth of embryo of about four weeks, outer side; vc, vesti- bular and cochlear portions ; rl, recessus labyrinthi. B, left labyrinth with parts of facial and auditory nerves of embryo of about four and a half weeks ; rl, reces- sus labyrinthi; use, psc; esc, superior, posterior, and external semicircular canals; s, saccule; c, cochlea; vn,fn, vestibular and facial nerves; vg, eg, gg, vestibular, cochlear, and geniculate ganglia. C, left labyrinth of embryo of about five weeks, from without and below ; labelling as in preceding figure. The opposite, anterior or ventral extremity of the otic vesicle also bulges out into a small evagination, which grad- ually elongates until it is a tapering tube, slightly curved inward toward the median plane. This lengthens still more and becomes spirally coiled, forming the cochlear duct or scala media of the future cochlea (Fig. 168). The vesicle itself becomes constricted in such manner by an inward pro- jection of its wall as to indicate its division into an upper larger and a lower smaller sac, the terms upper and lower referring respectively to the head-end and the tail-end of the embryonic body. Before the constriction occurs, the wall. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Heisler, Jo
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