Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 AUDITOR r AND VISUAL ORGANS. 85 In the Primates amongst the Mammalia there are present papilla; in the skin (especially on the volar surface) in which the structures known as touch-bodies, containing the termination of tactile nerves, are placed (fig. 82). In addition to the general sensibility and the tactile sensations, the higher animals possess, as a special form of sensibility, the capacity of distinguishing diffe
Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 AUDITOR r AND VISUAL ORGANS. 85 In the Primates amongst the Mammalia there are present papilla; in the skin (especially on the volar surface) in which the structures known as touch-bodies, containing the termination of tactile nerves, are placed (fig. 82). In addition to the general sensibility and the tactile sensations, the higher animals possess, as a special form of sensibility, the capacity of distinguishing different temperatures. The sensations of sound are produced through an organ, the auditory organ, which is, in a certain measure, a special modification of a tactile organ. The auditory organ in its simplest form appears as a closed vesicle filled with fluid (endolympfi) and one or more calcareous concretions (otoliths); and containing in its walls rod or hair cells in which the nerve fibrillse end (fig. 83). Sometimes the vesicle lies on a ganglion of the central ner- vous system (Worms), sometimes at the end of a shorter or longer nerve, the auditory nerve (Molluscs, Decapoda). In many aqua- tic animals the vesicle may be open and its contents communicate directly with the exter- nal medium, in which case the otoliths may be represented by small particles such as sand- grains which have entered it from the exterior (Decapod Crustaceans). In Molluscs a deli- cate sensory epithelium (macula acustica, fig. 83 Cz, Hz.\ marks the percipient portion of the inner wall of the vesicle; while in Crus- FlG- papi'.u from the volar surface tacea the fibres or the auditory nerve end in with the touch corpuscle cuticular rods or hairs which project from the and its nerve -v- wall of the vesicle, and, like the olfactory hairs of the antennae, bring about the nervous excitations. In the Vertebrata not only does the auditory vesicle obtain a more complicated form (mem- branous labyrint
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