Ixvili 
read before the Wernerian Natural History Society, and pub- 
lished in the Edinburgh Philosophical Journal, in April, 1823, 
has entered more fully into a comparison of the internal orga- 
nization of these two species, and has given the first account 
1 have met with, of the remarkable tracheal sac in the emu. 
His anatomical description, however, of this curious appendix, 
is brief and imperfect, which may be accounted for by the 
specimen he examined being greatly mutilated before it fell 
into his possession. His account of it is as follows :—** At 
the fifty-second ring, counting from the glottis, there is found 
a large muscular bag, about the size of a man’s head, into 
which the windpipe opens by a large orifice, occasioned by a 
deficiency of part of the circumference, in about thirteen tra- 
cheal rings; or rather the rings, instead of closing round to 
form the tube of the trachea, expand outwards, and are at- 
tached to the sides of the bag; it has no communication with 
any of the air cells’—p. 36. ‘* This muscular bag is as large 
as the human head, is closely attached to the sides of the 
trachea and expanded rings, is situated in the neck, immedi- 
ately above the bone called the merrythought; it was seen 
by me in the female, though it is probable the male also pos- 
sesses it. It is quite peculiar to this bird, no such appendage 
having been ever seen attached to the trachea of any of the 
feathered creation, nor do I know of anything analogous to 
it in any other animal, excepting in the chameleon, to the 
upper portion of whose trachea there is appended a compara- 
tively large membranous bag.”—p. 138. ‘It has not the 
most distant resemblance to the tracheal appendages found in 
other birds. In thus differing so singularly and mysteriously 
from the analogous structure of birds of the old and new con- 
tinents, it fully confirms the opinions of some naturalists, that 
the living productions of Australia will, when properly exa- 
mined, be found to present peculiarities altogether wonderful, 
and, perhaps, yet, for a long period, quite inexplicable.”— 
p. 139. 
