OCR Text |
Show 1874.] MR. A. H. GARROD ON THE AUSTRALIAN BUSTARD. 473 very similar in appearance, in closely allied birds, may be the result of different mechanisms. In the feet of the Cuculida and the Picidce the scansorial arrangement of the toes is the result of entirely different dispositions of the tendons which move them ; and in Otis tarda and Eupodotis australis the same reasoning holds. In both these birds there is, during the show-off, a distention with air of a well differentiated bag, which is in both cases lined with a true mucous membrane. But in Otis tarda this sac is a special structure in front of the windpipe, opening under the tongue ; whilst in Eupodotis australis (in the specimen under consideration at least), it is simply a highly dilated oesophagus. Through the kindness of Lord Lilford I am in possession of an excellent Spanish specimen of the gular pouch of Otis tarda (see fig. 1, p. 472), with the whole of the oesophagus, the tongue, and part of the trachea attached. In it the gular pouch, opening sublin-gually, is capacious, and, when distended, egg-shaped with no constriction in any part. The oesophagus is uniformly cylindrical for its upper two thirds, and not at all enlarged. Lower down there is a well-developed globular crop. In the specimen of Eupodotis australis which died on May 11, as previously mentioned, there is no trace of a gular pouch. The oesophagus is enormously dilated from its commencement (see fig. 2, p. 472), and gives no indication whatever of any division into tube and crop. Its greatest circumference, when fairly inflated, is 14 inches, and the length of the distended portion of the tube is \7\ inches. Before dissection, by filling its cavity with air, the lower portion of the dilated oesophagus protruded downwards considerably in front of the, symphysis furcula, and formed the depending portion of the sac which was so conspicuous in the living animal. The trachea descended in front of this sac ; and when the latter was undistended, the former, on account of the diminished distance between the points it had to reach, was zigzagged from side to side in the part opposite the pendent portion. The keeper, J. Church, tells me that, when handling the sac in the living bird, he always felt a hard cord running down in front of it, which was evidently the windpipe. The dilated oesophagus was, as might have been expected, covered with two coats of muscular tissue, the outer longitudinal-and the inner transverse. The mucous lining presented no peculiarities. The skin in front of the neck was lax, with a considerable amount of coarse fat in its deeper layer; it was engorged with blood, tortuous vessels running through it in all directions. I may mention as an anatomical peculiarity of interest that Eupodotis australis and E. denhami possess but one carotid artery, the right-a condition I have not seen in any other bird ; Otis tarda and O. macqueeni have two, and Tetrax campestris the left only. Most probably the presence of a right carotid only is characteristic of the genus Eupodotis. PROC. ZOOL. Soc-1874, No. XXXI. 31 |