306 Mr. Yarrell on the Organs of Voice in Birds. 



particles of food passing into the windpipe; but the surface near 

 the opening is furnished with numerous papilla?, pointing back- 

 wards, which assist in directing and conveying food towards and 

 into the oesophagus. 



Tab. XVII. Fig. 1. is a representation of the glottis with its 

 surrounding membranes. Fig. 2. is a representation of the car- 

 tilages forming the superior larynx. The letters, a, a refer to 

 the principal cartilage, which, when in its natural situation, lies 

 upon the pharyngeal portion, and between the cornua, of the os 

 hyo'ides or bone of the tongue. This cartilage appears to perform 

 the double office of the thyroid and cricoid cartilages in the 

 higher animals. In substance it is uniformly thin, its shape 

 nearly triangular, one angle placed forwards, the lateral angles 

 curving upwards to support the base of the arytenoid cartilages 

 on its own side. The letters b, b refer to the arytenoid cartilages, 

 supported at their base by the lateral angles of the cricoid car- 

 tilage before mentioned, and projecting forwards in two narrow 

 and thin parallel processes over two-thirds of the orifice formed 

 by the curved lateral portions of the cartilage underneath : each 

 parallel process forming a slight groove on its superior surface 

 by the edges curving upwards. 



The glottis is closed by a pair of muscles, (Tab. XVII. Fig. 4, 

 a, a) extending from the upper portion of the cricoid cartilage 

 along the crura of the arytenoid cartilages, upon each outer edge 

 of which they ar« inserted ; and it is opened by a pair of muscles 

 arising from the lateral and posterior portions of the cricoid 

 cartilage, the fibres of which passing over the pair of smaller 

 muscles just described, are inserted upon the inner edge of 

 each arytenoid cartilage (Fig. 3, b, b). The obvious use of 

 these two pair of muscles is to govern the size of the aper- 

 ture. Baron Cuvier in his Lemons d' Anatomic Comparee, vol. iv. 

 p. 490, says, "Birds have no arytenoid cartilages;" but the 



uses 



