. A text-book of embryology for students of medicine [electronic resource]. Embryology; Embryology. 346 TEXT-BOOK OF EMBRYOLOGY. and the external ear act as media for the conduction of sonorous vibrations. The internal ear being the esssential part of the organ of hearing and being also the part first formed may properly receive first consideration. The Internal Ear.—The membranous labyrinth of the. Fig. 166.—Three transverse sections showing development of otic vesicle of human embryo (Tourneux): A, from embryo of 3 mm., showing auditory pit; B, from embryo of 4 mm., showing the transformatio
. A text-book of embryology for students of medicine [electronic resource]. Embryology; Embryology. 346 TEXT-BOOK OF EMBRYOLOGY. and the external ear act as media for the conduction of sonorous vibrations. The internal ear being the esssential part of the organ of hearing and being also the part first formed may properly receive first consideration. The Internal Ear.—The membranous labyrinth of the. Fig. 166.—Three transverse sections showing development of otic vesicle of human embryo (Tourneux): A, from embryo of 3 mm., showing auditory pit; B, from embryo of 4 mm., showing the transformation of the pit into the otic vesicle; C, from embryo of 6 mm., showing otic vesicle detached from surface ectoderm, and presenting a posterior diverticulum, the recessus vestibuli. internal ear is the oldest part of the organ of hearing. Its origin is from a thickened circular patch of ectoderm on the dorsolateral surface of the head-region of the embryo near the dorsal termination of the first outer visceral furrow. The thickened area sinks below the surface, forming thus the auditory pit, which is present in the third week (Fig. 166, A). The pit becomes deeper, its edges approach each other and finally meet and unite to form the otic vesicle or otocyst. This little epithelial sac gradually recedes from the surface ectoderm. At this stage of development there is no cranial capsule other than the indifferent mesodermic tissue which surrounds the brain-vesicles; hence, the otic vesicle, em- bedded in this tissue, lies in close proximity to the after- brain, and comes into relation with the acusticofacial gan- glion (p. 321). The vesicle, at first spherical, soon becomes. 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, John Clement; Waterstone, David, former owner; Duke-Elder, Stewart, 1898-1978, fo
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