" 
308 Mr. YARRELL on the Organs of Voice in Birds. 
cal, or triangular at its lower surface, (Tas. XVII. Fig. 7, 11, 
& 12) having a central cross-bone extending from behind to the 
front, dividing the orifice in two equal parts (Fig. 11 & 12, a,a) ; 
to the outer side of which cross-bone the inner membrane of 
each bronchial tube is attached. This cross-bone thus dividing 
the lower orifice, forms the point of divarication from which the 
bronchiz arise separate, and go off to the lungs. But a more 
minute description of this important part will be given, when 
considering the various muscles connecting the bone of divari- 
cation with the bronchie. | 
— The bronchie are formed on the outer sides by membrane 
interposed between and connecting a variable number of carti- 
lages which describe only parts of circles, diminishing in size as 
they approach the lungs, the circle being completed on the 
inner side by a delicate membrane stretching from the opposite 
points of the semicircular cartilages, and forming a tube from 
the orifice of the inferior larynx to the substance of the lungs 
(fas. XVII. Fig. 9 & 10, c, c). This membrane is called by 
Cuvier the membrana tympaniformis, and upon its dilatation and 
contraction, as well as the power afforded of altering the form 
and length of the bronchiz, some of the varieties of intonation 
depend. The bronchiz are p.slee slightly attached to each other 
: Se ca mtm ey 
he muscles of the glottis or superior larynx are uniformly 
tvo pair in all the birds i. ean examined: but the mt 
of the inferior or true larynx, all largely piscis with nerves, 
vary from one pair to five pair, according to the genus or spe- 
cies, affording a corresponding increase in the various qualities 
of the voice. Some few birds have no true muscles of voice at 
the inferior portion of their trachez. Cuvier describes the 
King of the Vulture as is being without any ; and this is also the 
case with the Condor. Tas. XVII. Fig. Se is a representation 
| of 
