ORGAN OF HEARING IN BIRDS. 



133 



when, finding nothing eatable, the bird flew away. Hence the 

 American ornithologist concludes that the Vulture is led to its 

 game by sight alone. But the truer deduction may be that 

 having always received impressions from sight, combined Avith 

 and confirming those, in some cases the first received, from smell, 

 the Vulture was unwilling to disbelieve its own eyes, thouo-h the 

 odour was absent. It may .often have been led by sight to the 

 carcass of a dying beast, or one dead too soon for any putre- 

 factive emanations to have escaped, and so it mistook the stuifed 

 deer for a recently dead one. In a converse experiment, a dead 

 hog being concealed in a ravine, and covered with briers and 

 cane, ^ many Vultures were seen from time to time sailing over 

 the spot where the putrid carcass was hid,' but none of them 

 attempted to expose it ; whilst several dogs found their way to it, 

 and devoured the flesh.' ^ The right inference from this experi- 

 ment is, that the Vultures were attracted by the putrefactive 

 effluvia; but, having always associated sight with smell, and 

 having neither the burrowing power of the dog, nor the habit of 

 hunting exclusively by scent, they were baffled. 



§ 143. Organ of Hearing. — The general character of this 

 organ resembles that in Reptilia, but, as Hunter well remarks, 

 ' there is a neatness and precision in the 

 structure which is not to be found in the 

 Tricoilia^'^ The whole of the primitive 

 cartilaginous acoustic capsule is ossified 

 and confluent with contiguous elements 

 of cranial vertebra?, and there is a better 

 defined and usually deeper fossa or ' mea- 

 tus ' external to the ear-drum. In most 

 Birds a fold of integument projects from 

 the fore part of the meatus ; this is largest 

 in the Owls, but the ear-drum is not pro- 

 tected by one so developed as to form a 

 conspicuous ^ conch' or ^ auricle.' At most, 

 in some Birds, as the Bustard, fig. 54, d. 

 Ostrich and Owls, particular feathers are 

 so developed and arranged around the 

 meatal margin, as to serve the office of an 

 external ear : the auricular feathers beino^ 

 raised and directed so as to catch and concentrate the vibrations 

 of sound that may have excited the bird's attention. 



54 



Head and auricle of Bustard, with 

 cervical air-cell, xxxiii-. 



' XXXII-. vol. ii. p. 34 ; vol. v. p. 345. 



Vol. i. p. 208. 



