. On the anatomy of vertebrates [electronic resource] . ed from the backof the nose or mouth to thetympanum. In passingthrough this tube the air iswarmed, and a proper at-mosphere maintained in frontof the membranous parts ofthe walls of the labyrinth. The structure of the ear-organ in Cetacea is highly suggestiveand interesting: it is, as Hunter remarks, c upon the same prin-ciple as in the quadruped; 168yet the outer opening andpassage leading therefromto the tympanum can rarelybe affected by sonorous vi-brations of the atmosphere,and indeed they are re-duced, or have degenerated,to a degree
. On the anatomy of vertebrates [electronic resource] . ed from the backof the nose or mouth to thetympanum. In passingthrough this tube the air iswarmed, and a proper at-mosphere maintained in frontof the membranous parts ofthe walls of the labyrinth. The structure of the ear-organ in Cetacea is highly suggestiveand interesting: it is, as Hunter remarks, c upon the same prin-ciple as in the quadruped; 168yet the outer opening andpassage leading therefromto the tympanum can rarelybe affected by sonorous vi-brations of the atmosphere,and indeed they are re-duced, or have degenerated,to a degree which makes itdifficult to conceive howsuch vibrations can be pro-pagated to the ear-drumduring the brief momentsin which the opening maybe raised above the a full-sized Cachalot itis a longitudinal slit oneinch in length, admittingwith difficulty the end ofthe fore-finger. In our com-mon porpoises and dolphinsthis opening is so small asto require search in detect-ing, fig. 168, a : it leads toa flexible membranous canalcapable of receiving,. Organ of hearing, Del pi nat . size. xx. 224 ANATOMY OF VERTEBKATES. Delphinus tursio, a hogs bristle: having passed through the skinand blubber, it makes a sudden bend upon itself, at b, and is thencontinued by a course of about an inch and a half to the ear-drum,where it rather suddenly expands: in the subcutaneous part ofits course the walls are strengthened by a few longitudinal carti-lages with elastic connections, allowing of slight changes in lengthand disposition; but the walls are in contact throughout most ofthe narrow part of the tube. The ear-drum is concave exter-nally in Delphinidce and Physeteridcs ; but in a BalcenopteraHunter found it projecting with an unusual degree of convexityinto the dilated inner termination of the meatus. The density of the osseous tissue of the tympanic bone, ib. c,recalls that of the large otolites of fishes, and the almost freesuspension of this singularly shaped subconvolute mass sugge
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