On the development of the membranous labyrinth and the acoustic and facial nerves in the human embryo / by George L. Streeter.

  • Streeter, George Linius, 1873-1948.
Date:
[1907]
Catalogue details

Licence: In copyright

Credit: On the development of the membranous labyrinth and the acoustic and facial nerves in the human embryo / by George L. Streeter. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    This investigation was originally concerned only with the acoustic complex, later it was extended to the ear vesicle, and it was found possible to add several new features concerning the development of this structure and the formation of the membranous labyrinth to that which was already known from the work of His, Jr., 89, who, as far as could be learned, is the only investigator that has made a direct attack on this region in the human embryo since the introduction of wax plate reconstruction methods. It is, of course, to be remembered that in his work attention was mainly directed toward the nerve and ganglion masses, while the finer structure of the ear vesicle was not considered in detail. The contributions here reported include both additional early stages in the development of the ear vesicle and further details in the formation of the individual parts of the labyrinth. Also some apparently funda- mental errors in the work of the above investigator have been here corrected. One of these regards the saccule, which as represented by His, Jr., develops as a compartment pocketing out from the upper end of the cochlea, but which in our specimens develops as a com- partment or subdivision of the utricle. Instead of the saccule developing from the cochlea, the cochlea develops from the saccule, though this occurs at a considerable time before the separation between utricle and saccule is complete. The facial nerve, and especially its sensory division or pars intermedius, bears such a close relation to the auditory apparatus that it was found convenient to include it in some of the reconstructions. It was possible to identify conditions in the embryo confirmatory of what is now the generally accepted opinion as regards the adult, i. e., that the nervus intermedius is the dorsal and sensory root of the seventh, its fibers arising in the geniculate ganglion and continued peripherally in the chorda tympani and great superficial petrosal. Material and Methods. This work was made possible through the kindness of Professor Mall, who gave the writer, for the purpose of this investigation, free access to his large collection of human embryos. In the following list are tabulated the embryos which were selected for reconstruction: