. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. AUDITOEY ORGAN 221 of Vertebrates is situated in the region of the head, between the origins of the trigeminal and vagus nerves. After the vesicle of each side has become separated off from the epiblast and connected with the brain by means of the auditory nerve (which arises in coimection with a peripheral ectodermic ganglion and then grows centripetally to the brain), it sinks deeper and deeper into the mesoblastic tissue of the skull: it then loses its original pyriform or rounded shape, and becomes divided into two
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. AUDITOEY ORGAN 221 of Vertebrates is situated in the region of the head, between the origins of the trigeminal and vagus nerves. After the vesicle of each side has become separated off from the epiblast and connected with the brain by means of the auditory nerve (which arises in coimection with a peripheral ectodermic ganglion and then grows centripetally to the brain), it sinks deeper and deeper into the mesoblastic tissue of the skull: it then loses its original pyriform or rounded shape, and becomes divided into two parts, called re- spectively the utrimdus and sacculus (Fig. 177). From the former. Fig. 178a.—Isolated Elements of the Memkrakous Labykinth of various Vertebrates. (After G. Retzius.) A, from the macula acustica communis of Myxine glutinosa ; B, from the macula acustlca neglecta of Raia clavata ; C, from the crista acustica of an ampulla of Linedon {Amhlystoma) mexicanux ; D, from the crista acustica of the anterior ampulla of Roma esculanta. hz, hair-cells with auditory hairs {h); fz, thread-like cells; n,n, dividing nerve. On the left side of D the auditory hair has become broken up into its con- stituent fibres. the semicircular canals become developed, while from the latter the tube-like duchis enclolymphatictis and the lagena {cochlea) are formed. The whole of this complicated apparatus constitutes the internal ear or memhranous labyrinth. It becomes surrounded secondarily by mesoblastic tissue, with which it is at first in close contact. A process of absorption then takes place in the innermost layers of the mesoblast, and thus a space is developed which closely. 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 Wiedersheim, Robert, 1848-1923; Parker, William Newton, 1857-1923. London, Macmillan
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
