. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 434 THE INTERNAL EAR may be seen from Fig. 256, which represents the condition occurring in an embryo of mm. A short distance below the level at which the canals communicate with the remaining portion of the otocyst a constriction appears, indicating a separation of the otocyst into a more dorsal portion and a more ventral one. Later, the latter begins to be prolonged into a flattened canal which, as it elongates, becomes coiled upon itself and also becomes separated by a constriction fr
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 434 THE INTERNAL EAR may be seen from Fig. 256, which represents the condition occurring in an embryo of mm. A short distance below the level at which the canals communicate with the remaining portion of the otocyst a constriction appears, indicating a separation of the otocyst into a more dorsal portion and a more ventral one. Later, the latter begins to be prolonged into a flattened canal which, as it elongates, becomes coiled upon itself and also becomes separated by a constriction from the remaining portion of the otocyst (Fig. 257). This canal is the ductus cochlearis (scala media of the cochlea), and the remaining portion of the otocyst sub- sequently becomes divided by a con- striction into the utriculus, with which the semicircular ducts are connected, and the sacculus. The constriction which separates the cochlear duct from the sacculus becomes the ductus re- uniens, while that between the utri- culus and sacculus is converted into a narrow canal with which the ductus endolymphaticus connects, and hence it is that, in the adult, the connection between these two portions of H the otocyst seems to be formed by the ductus dividing proximally into two limbs, one of which is connected with the utricle and the other with the saccule. When first observed in the human embryo the auditory ganglion is closely associated with the geniculate ganglion of the seventh nerve (Fig. 255, B), the two, usually spoken of as the acustico-facialis ganglion, forming a mass of cells lying in close contact with the. Fig. 256.—Reconstruction of the Otocyst of an Embryo of MM. co, Cochlea; de, endolymphatic duct;.sc, semicircular duct.—(His Jr.). 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 McMurr
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