VOICE. 



1497 



seven rings of the trachea. It is divided 

 within into two unequal cavities by the os 



Fig. 914. 



2. 



1. 



wards perpendicularly to the axis of the the developement and union of the last six or 

 bonchus of the same side, by which means 

 the area of the latter is varied. 



The third bone is but very slightly curved 

 (r). It is separated from the second bone by a 

 triangular membrane; having its extremities 

 articulated to the second bone by ligaments 

 which permit of an extensive freedom of mo- 

 tion, particularly of a rotatory movement on 

 its axis, and it is an important agent, accord- 

 ing to Savart, in modulating the voice. The 

 internal surface of this bone is lined with a 

 fibrous cord which forms the external lip of 

 the glottis. The posterior extremities of 

 these three bones are not united, but have a 

 triangular space between them for the passage 

 of the oesophagus. 



Fis. 913. 



a 



Inferior Larynx of the Haven, 

 Shewing the three bones, a, b, c. 



The Membrana tympaniformis. This is a 

 thin transparent membrane, extending from 

 the os transversale to the extremities of the 

 bronchial half- rings g (figs. 912 and 914) : it 

 forms the internal surface of the larynx and 

 bronchi, and is a continuation of the semilunar 

 membrane; so that the tympaniform and 

 semilunar membranes are stretched simul- 

 taneously, and the latter is acted upon through 

 the instrumentality of the former. 



The Arytenoid Cartilage. This is a small 

 body situated at the head of the second bone : 

 it is described by Savart as being of a lozenge 

 shape in the starling, but very short in the 

 nightingale. This form of larynx in the Cor- 

 vidae and Sylviadae is provided with six pairs 

 of muscles.* ( See /g. 914.) 



Palmipedes. In the genera Anas and 

 Mergus the inferior larynges of the males only 

 are unsymmetrical, and composed of bony ca- 

 vities. In the Anas domes ticus, the inferior 

 larynx presents osseous cavities formed by 



* These muscles are given in detail by Savart, 

 Memoirs sur la Voix des Oiseau.r, in the Ann. de Chem. 

 et de Physique, vol. xxxii., also Cuvier, in the Rt-yne 

 Animal, vol. iv. There are five pairs of muscles as- 

 signed to the inferior larynx of the singing birds by 

 Cuvier, Mr. Yarrell, Professors Grant and Owen, but 

 six can be made out in the Corvidre, as stated by 

 Savart, and seen in the figure of the Kaven. 



1. The inferior Larynx of the Raven, 



Shewing the six muscles, a, b, c, d, e.f, which mo- 

 dulate the voice on one side. 



2. Anterior vieiv of the same, 

 Shewing the membrana tympaniformis, g. 



transversale, of which the left is always the 

 largest. The figure of the os transversale is 

 very similar to that of the arytenoid cartilage 

 in the human larynx, consisting of prominences, 

 ridges, and base : the superior prominence of 

 this bone projects high into the tube of the 

 trachea, and completely divides the larynx at 

 its base. The ridge on its left side is fur- 

 nished with a salient lamina, corresponding to 

 a thin transparent semilunar lamina, situated 

 opposite to it : the latter is placed at the en- 

 trance of a small osseous cavity at the infe- 

 rior boundary of the left larynx; a still larger 

 osseous cavity lies obliquely above the semi- 

 lunar membrane. The air sets this membrane 

 in motion as it circulates in the left chambers 

 of the larynx, and contributes to the produc- 

 tion of the well-known peculiar character of 

 voice in this bird. On the right side the 

 cavity of the larynx is of smaller dimensions, 

 of less irregular form, and destitute of those 

 prominent ridges and salient lamina? within. 

 There appears to be a small tympanic mem- 

 brane attached to the first few rings of the 

 bronchus on the right side. 



In the Mergus serrator the inferior larynx 

 is partly osseous, and partly membranous : it 

 consists of two irregular cavities. The os 

 transversale, i(fg- 915), which has an exten- 

 sive union along its posterior edge and base 

 with the bony boundaries of the larynx, divides 

 this tube into two parts, except at its superior 

 prominence, where it leaves a channel b 

 for the air from the right bronchus J\ to pe- 

 netn.te the trachea. On the right lateral 

 surface of the larynx, a large oval membrane 



