498 MANUAL OF ZOOLOGY. 



of simple perforations, which sometimes communicate from 

 side to side by the deficiency of the septum narium. In the 

 singular Apteryx of New Zealand, the nostrils are placed at the 

 extreme end or tip of the elongated upper mandible. Some- 

 times the nostrils are defended by bristles, and sometimes by a 

 scale (Rasores}. Taste must be absent, or almost absent, in 

 the great majority of birds, the tongue being nothing more than 

 a horny sheath surrounding a process of the hyoid bone, and 

 serving for deglutition or to seize the prey. In the Parrots, 

 however, the tongue is thick and fleshy, and some perception 

 of taste may be present. Touch or tactile sensibility, too, as 

 already remarked, is very poorly developed in Birds. The 

 body is entirely, or almost entirely, covered with feathers ; the 

 anterior limbs are converted into wings, and rendered thereby 

 useless as organs of touch ; and the posterior limbs are covered 

 with horny scales or feathers. The bill certainly officiates as 

 an organ of touch, but it cannot possess any acute sensibility, 

 as in most birds it is encased in a rigid horny sheath. In some 

 birds, however, such as the common Duck, the texture of the 

 bill is moderately soft, and it is richly supplied with filaments 

 of the fifth nerve ; so that in these cases the bill doubtless con- 

 stitutes a tolerably efficient tactile organ. The " cere," too, 

 or the fleshy scale found at the base of the bill in some birds, 

 is in all probability also used as a tactile organ. 



The last anatomical peculiarity of Birds which requires 

 notice is the peculiar apparatus known as the "inferior 

 larynx," by which the song of the singing birds is conditioned. 

 "The air-passages of birds commence by a simple superior 

 larynx, from which a long trachea extends to the anterior 

 aperture of the thorax, where it divides into the two bronchi, 

 one for each lung. At the place of its division, there exists in 

 most birds a complicated mechanism of bones and cartilages, 

 moved by appropriate muscles, and constituting the true organ 

 of voice; this part is termed the inferior larynx" (Owen). 

 The structure of the vocal apparatus is extremely complicated, 

 and there is no necessity for entering upon it here. It is to be 

 remembered, however, that those modifications of the voice 

 which constitute the song of birds, are produced in a special 

 and complex cavity placed at the point where the trachea 

 divides into the two bronchi, and not in a true larynx situated 

 at the summit of the windpipe. Lastly, the trachea of birds is 

 always of considerable proportionate length, and it is often 

 twisted or dilated at intervals, this structure, doubtless, having 

 something to do with the production of vocal sounds.* 



* The student desirous of fuller information as to the anatomy of Birds 



