1498 



VOICE. 



forms the boundary : the rest of this cavity is 

 composed of bone. On the left side the 

 larynx is furnished with four membranes, of 

 unequal dimensions, which are inclined to each 

 other at different angles ; of these membranes 

 three are lateral, and the fourth forms the 

 base. The internal lateral membrane b lies 

 almost parallel to the superior promontory of 

 the os transversale i, from which it is separated 

 by a channel, leading from the left to the right 

 larynx .* Through this channel the air from the 

 left bronchus must pass to reach the trachea. 

 The internal lateral membrane has a free salient 

 edge inferiorly, over which the air brushes in 

 its passage from the lungs to the trachea.f 

 The posterior, anterior, and lateral mem- 



branes are supported by bony rings, of which 

 the anterior is the largest. The membrane 

 forming the base is penetrated by the left 

 bronchial tube, and is connected with several 

 of the bronchial rings through the medium of 

 the membrana tympaniforrnis. Thus the air 

 from the lungs throws into vibration one 

 large membrane in the right, and four in the 

 left laiynx, all of unequal dimensions, and con- 

 stituting a very complex piece of mechanism. 

 In the M. Merganser or Goosander the 

 inferior larynx is most developed on the 

 left side h (Jiff. 916), which is chiefly mem- 

 branous, while the other side d is composed 

 principally of bone. On the left side there 

 are four irregular membranes, a, b, c, supported 



Fig. 915. 



Two views of the Inferior Larynx of the Mergus Serrutor. 



by bones, and that on the external ring h. 

 The os transversale is very small and does 

 not reach the free edge of the internal mem- 

 brane b, which is similar to that of the 

 Atergns serrafor, thus leaving a communi- 

 cation open between the right and left side of 

 the cavity of the larynx, through which the 

 air from the left lung must pass to reach the 

 tube of the trachea, which terminates on the 

 superior part of the right side of the larynx. 

 The right side is chiefly surrounded by bone 

 externally, having a very small oval membrane 

 anteriorly, and is furnished with a small 

 tympanic membrane at its junction with the 

 bronchus. The salient portions of these 

 membranes, and the small membrana tym- 

 paniformis are best adapted for putting the 

 air into a state of vibration, reinforced by 



* The area of this channel is increased by an 

 osseous cavity which is formed by the posterior "con- 

 cave surface of the ridge g, lying externally in 

 front of the larynx. 



f Beneath the inferior point of attachment of the 

 internal lateral membrane, the above-mentioned 

 conical osseous cavity passes vertically downwards c 

 terminating between the bronchi in a kind of cul 

 de sac. 



the chambers of which the larynx is com- 

 posed. 



Fis. 916 



Inferior Larynx of the M. Merganser. 



