IO 



CASSELLS BOOK OF BIRDS. 



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sailing in all directions over the spot where the putrid carcase was lying covered only with twigs of 

 cane and light underwood, none of them appeared at all to suspect its presence. 



Nevertheless, notwithstanding the apparently decisive result of the above experiments, anatomy 

 teaches us that the olfactory apparatus in this class of animals is largely developed, and indicates by 

 its extent that it is well adapted to investigate the odorous properties of the air taken in for 

 respiration. 



The sense of hearing in birds is remarkably acute, as might be readily inferred from the vocal 

 capabilities conferred upon many of these gifted songsters. Their music is certainly not less appre- 

 ciated by the performers than it is by their auditors. " Nobody can doubt," observes Bishop Stanley, 

 " who sees a bird singing, clapping its little wings, turning from side to side, and glancing its bright 

 eyes in all directions, as if courting attention and admiration, that it feels delight and satisfaction. 



Did we require further proof, we have but to 

 recollect that the song-bird is most alert with 

 the music of its voice when its affections and 

 interests are awakened by its mate during the 

 time of rearing its young." It is, indeed, prin- 

 cipally during the breeding-season that the 

 singing power of birds is in full activity; and 

 seeing that in general it is only the male that 

 possesses the musical faculty, we may naturally 

 suppose that its exercise is intended for the 

 solace and amusement of his mate during 

 her confinement to her nest. The nightingale 

 himself becomes voiceless so soon as the ap- 

 pearance of his nestlings calls him to more 

 profitable employment. 



It is, however, among the nocturnal birds 

 that the faculty of hearing is more specially 

 developed. In the generality of birds there is 

 no provision made externally for catching or 

 concentrating sonorous impressions ; but in the 

 owls, the bustards, and a few others that venture forth at night, we find a different arrangement. 

 In the owls, more especially, an external auditory apparatus is very conspicuous ; not only does the 

 integument exhibit a variety of folds, the disposition of which forcibly reminds us of the human ear, 

 but the feathers upon the sides of the head are so disposed as to fulfil in some degree the purposes of 

 a hearing trumpet. (See Fig. 8.) In such species the sense of hearing is exquisitely developed. 



In the generality of birds the sense of taste can scarcely be said to exist. The manner in 

 which they obtain and swallow their food precludes the possibility of enjoyment from this source, so 

 that their tongue is in many cases appropriated to some totally different use. In by far the greater 

 number the tongue is small, thin, and cartilaginous ; the extremity is flat, and incapable of being 

 protruded beyond the bill. (See Fig. 9.) There are, however, great varieties in the construction of 

 this organ, a few of which will require our notice. 



The tongue of the parrot, although its substance is not so fleshy, has some resemblance to that 

 of man, and it is probable that this is one of the circumstances enabling these birds to imitate the 

 human voice with so much facility. 



In the family of the toucans and some others, the tongue, without being extensible, is fully as 



Fig. 8. — EXTERNAL EAR OF A YOUNG OWL. 



a, the Upper Part of the Head, partially denuded of feathers ; /', the Beak ; 

 d, the Eye ; e, e, f, Marginal Fold of Skin surrounding a cavity, the 

 interior of which somewhat resembles the folds of the human ear ; 

 g, Auditory Passage leading to /i, the Drum of the Ear {membrana 

 tympani). 



