. The structure and life of birds . ed Pigeon,whose plumage is a light blue-gray, has eyes of a richscarlet, just the colour of holly-berries. For the firstfew months of his life, the Gannets eyes are almostblack, but they soon turn to a pale, almost white, hue,long before he has exchanged the dusky-gray attire ofhis youth for the snow-white of his maturity. As a rulethe Iris is brown in young birds. The brighter tintscome with adult years, and in some species they arelimited to the The Ear. I shall first briefly describe the main features of thehuman ear, then point out the chief diffe
. The structure and life of birds . ed Pigeon,whose plumage is a light blue-gray, has eyes of a richscarlet, just the colour of holly-berries. For the firstfew months of his life, the Gannets eyes are almostblack, but they soon turn to a pale, almost white, hue,long before he has exchanged the dusky-gray attire ofhis youth for the snow-white of his maturity. As a rulethe Iris is brown in young birds. The brighter tintscome with adult years, and in some species they arelimited to the The Ear. I shall first briefly describe the main features of thehuman ear, then point out the chief differences betweenit and the same organ in birds. The essential partis in the sidewall of the skull ; and here there is a bony labyrinth consisting of three winding tubes of bone,which are filled with fluid (L, in fig. 33). There is 1 Dr. Gadow (Newtons Diet, of Birds, vol. i., p. 230) refers toa paper on this subject by Th. A. Bruhin in Zool. Garten, 1870,pp. 290-295, which I have not read. K 2 32 THE STRUCTURE AND LIFE OF BIRDS Fig. 33. {a) Human ear—diagrammatic ; (?>) ear of Owl, after Gadovv ; (c) of Thrush, after Retzius. c, Columella ; cch, Cochlea; e, Eustachian tube ; ex, outer opening of Ear ; L, Labyrinth; Lg, Lagena ; m, Membrane, closing the drum ; n, entrance of auditory nerve; nn, Nerve endings; 01, 2, 3, the three Ossicles, Stapes, Incus, Malleus; ft, Pterygoid bone. vi FORM AND FUNCTION 133 also a great extension, called, because it is shaped likea spiral shell, the cochlea, and into this too thefluid extends. A membranous bag, also filled withfluid, extends throughout the ramifications of thecochlea and the labyrinth. On the inside of themembranous bag within the labyrinth, at certainpoints where it is attached to the bony wall, are hairswhich are believed to communicate with the nerve ofhearing. So far, 1 have been describing the earproper. The rest of the machinery has for its objectthe communication of the vibrations of sound to thefluid in the bony
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