iSSs-] Kitchen o>i the Inferior Larynx in Birds. 2Q 



sound produced by the double concave, perforated tin mouth- 

 piece of the children's toy that is frequently seen. This rim, by 

 its vibrations when articulated by the highly developed tongue 

 of the Parrot, produces the nearest approach to human singing 

 of which birds are capable. Of course the much repeated ditty 

 of a trained Polly is nearly destitute of variation in the pitch of 

 the tones produced, any range in this respect being produced by 

 differences in the strength of the air-blast, distension of the 

 trachea, and change in shape of the mouth cavity. There is no 

 muscular apparatus furnished for making any tension on the ex- 

 tremities of the rim of the glottis in birds. 



The inferior larynx, or syrinx, is an organ peculiar to birds. 

 Its parts are merely a different evolution and functional develop- 

 ment and modification of the cartilaginous rings, mucous mem- 

 brane, and muscular fibres seen in the trachea and bronchi of 

 mammals. The structure varies widely in different birds, being 

 most complex as a rule in the most able songsters. It may be 

 highly developed in birds which are not ranked among the 

 singers. This organ seems to have originally been called forth 

 as a secondary valve, acting as an auxiliary to the superior larynx 

 in closing the air passage leading to the lungs, during submersion 

 of the heads of the aquatic birds. In most Ducks the lower larynx 

 is expanded into an irregular bony case, divided into two unequal 

 cavities. These cavities would undoubtedly add resonance to 

 voice formed at the superior larynx. They would also act as a 

 float, tending to make the upper part of the chest more buoyant. 

 The inferior larynges in those birds examined by the writer are 

 so constructed that some of the parts are very delicate, thin, and 

 easily folded, thus enabling a closure of the air tract at this point 

 to be easily accomplished, even by a simple recession of the neck. 

 The bronchi are especially compressible and easily lacerated. 

 They are strengthened by half-rings on the outer side, the inner 

 being formed by a membrane that has been called the tnembrana 

 tympaniformis. In most vocal birds the syrinx has a double 

 glottis, one on either side of a bony bar, called the os transversale^ 

 which runs from before backward at the apex where the inner 

 suk-s of the bronchi join. It supports a thin membrane which 

 ascends into the trachea, and terminates in a thin, concave mar- 

 gin, called the membra na semilunaris. This is most developed 

 in singing birds, and being vibratile forms an important part of their 



