OCR Text |
Show 412 DR. J. MURIE ON THE EMU. [Apr. 1 1, lungs, without being necessitated to allow it to escape, in order to perform the act of inspiration" (ibid. pp. 136-139). Wedemeyer was inclined to regard it as an air-reservoir for oxygenizing the blood, as did Fremery. Meckel, in summing up the opinions of these authors, gives his own to this effect:-That it has no connexion with the voice, that more probably it facilitates running, and that in exceptional circumstances it may functionally answer as a swimming-bladder. Dr. Macartney advances the idea that " the peculiar sound belonging to the New Holland Ostrich is entirely occasioned by the reverberation or resonance produced in the membranous bag connected with the front of the trachea," giving analogous instances in the bird, horse, howling-baboon, and bull-frog. Professor Owen, as already mentioned, at least considers there is an existing relation between the sac and the sound. Dr. George Bennett* states, " the only sound emitted by the Emeu is a sort of hollow booming note. It is considered to be produced in the female by means of the expansion and contraction of a large membranous bag surrounding an oblong opening through the rings of the trachea." Mr. Bartlett, Superintendent of the Society's Gardens, has made many observations on the voices and habits of the Struthious Birds living in the Society's Menagerie. On discussing the mooted question of the use of the sac with him, he supplies m e with the following information : - " I have no reason to believe the sac and opening in the trachea in the E m u have anything whatever to do with swimming, breathing, or running, but I consider them as constituting simply the organ of sound employed by both male and female during the breeding-season. Probably at other times the sound produced by the female is louder and of a more regular drumming kind than in the male bird, also the lower part of the neck is inflated to a much greater extent in the female than in the male during the time these sounds are emitted. I am, moreover, unable to say whether the cavity is larger in the female than in the male." In offering m y own opinion upon the supposed function of this very remarkable tracheal appendage, unknown in any other species of bird, I must confess myself very undecided concerning its adaptation to one special use. Placing the opinions of the several authorities in a tabular form they may be stated as follows:- 1st. Respiratory purposes (oxygenation of the blood). 2nd. As a swimming-bladder. 3rd. As an air-reservoir in running. 4th. For simple vocal resonance. 5th. Sexual organ of sound during the breeding-season. With respect to the first of these assigned functions, this may be looked at in a twofold view. The sac may either be regarded as a membranous expanse, the vascularity of which permits it to deoxy-genize the inspired air, as does the lung; or it may merely supply the place of an air-reservoir to the lungs themselves. The first of * Gatherings of a Naturalist in Australia (London, 1860), p. 219. |