70 C'ORV^ID.E. 



broncliiae ; and the variety of modulation birds in general are 

 known to possess has its corresponding variety of forms and 

 appendages. The glottis, or superior larynx, opens into the 

 mouth at the root of the tongue. The orifice, figure 1, letter 

 6, in the first group of illustrations, is long and narrow, en- 

 circled by two pair of muscles, figvire 2, letters b, b, and 

 figure 3, a, a, which govern the size of the aperture, and con- 

 stitute one of the accessory means by which the sound of the 

 voice is regulated. Birds have no epiglottis, or covering 

 over this aperture, to prevent any particles of food passing 

 into the windpipe ; but the surface near the opening is fur- 

 nished with numerous papilla?, pointing backwards, which 

 assist in directing and conveying food towards and into the 

 oesophagus. 



Figure 1 is a representation of the glottis with its sur- 

 rounding membranes. Figure 4 is a representation of the 

 cartilages forming the superior larynx, all the softer parts 

 having been removed. The letters a refer to the principal 

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

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

 or bone of the tongue. This cartilage appears to per- 

 form the double office of the thyroid and cricoid cartilages 

 in the higher animals. In substance it is uniformly thin, 

 its shape nearly triangular when laid flat, one angle placed 

 forwards, the lateral angles curving upwards to support the 

 base of the arytenoid cartilage on its own side. The letters 

 b, b refer to the arytenoid cartilages, supported at their base 

 by the lateral angles of the cricoid cartilage, before men- 

 tioned, and projecting forwards in two narrow and thin paral- 

 lel 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 sur- 

 face by their edges also curving upwards. 



The glottis is closed by a })air of muscles, fig. S, a, a. 



