Mr. YARRELL on the Organs of Voice in Birds. — 918 
which go off about half-way between this bulb and the inferior 
larynx, to be inserted upon the os furcatorium. These muscles 
are called ypsilo-tracheal by Baron Cuvier, from the form of the 
bone upon which they are inserted. ‘They seem peculiar to 
those birds having enlargements of the tube, and figures of the 
two last-mentioned trachez will be found attached to Dr. La- 
tham's Paper in the 4th volume of the Transactions of the Lín- 
nean Society. 
I have mentioned the Gannet as differing from the Natatores 
generally in being provided with a second pair of true muscles 
of voice ; but the second pair in this bird differ materially from 
the furculo-tracheal muscles already described as existing in the 
three species of palmated birds having enlargements of the tube. 
The trachea in the Gannet is uniform in size throughout, and fur- 
nished with one strong pair of muscles, which, passing down the 
side of the tube nearly the whole of its length, go off to be in- 
serted upon the sternum as usual. Underneath and below these 
there is another pair given off from the inner surface of the first, 
which pass directly downwards, and are inserted upon the upper 
surface of a spherical glandular protuberance fixed to the upper 
or first half-circular bronchial cartilage. The membranous divi- 
sion between the point or bone of divarication and this first ring 
is considerable ; and the contraction of this second pair of mus- 
cles shortens the bronchiz the whole depth of this division, pro- 
ducing at the same time corresponding tension of the membrana 
tympaniformis. The protuberances upon the bronchiz here no- 
ticed are solid, unctuous in appearance, and probably perfor 
the office of bronchial glands. Tas. XVIII. Fig. 4, & 5, repre- 
sent the lower portion of this trachea in two points of view. 
Trachez possessing three pairs of true muscles of voice are 
confined entirely, as far as my observations have extended, ito 
one very large family only, the Psittacide ; and these: muse e 
ui 2s42 pc will 
