The inferior larynx, the true situation' nf the organ of
voice in birfis, as the experiments of Baron Cévier have sufficiently
proyed, is situated at the bottom of the tube, and is
formed sometimes, by the approximation, of several of the
lower rings of the trachea more or less firmly ossified toge-
ther, and occasionally of solid bones ; varying in' form, being
compressed, conical, or triangular at its. lower surface, figs.
4 and 5, a and b, of the second group, having a central cross-,
bone, figs. 4 and 5, a, a, extending from behind to the front,
dividing'the orifice into two equal parts ; to the miter side of
which cross-bonehhe inner membrane of each bronchial tube
is .attached. ' This cross-bone,-th,us- dividing the orifice,'forms
thé’point of divarication from which the bronchise arise separate,
and go off to the; lungs.. But a more mintite description
of this important part will be given, when considering
the various ‘muscles connecting the tube', thé bone of divarication,
and the bronchise.
The' bronchial tubes are formed on- thé outer sidek by
paeihbrane ' interposed between, and connecting a variable
number of cartilages, which describe only parts of circles, diminishing
in size as they approach the lungs, fig. % c, the
circle b'éing completed ott thé inner side by a delicate membrane
stretching from tKeiopposite points of thé semi-circular
cartilages, fig. 3* c, and forming a tube from the orifice of thé
inferior larynx to 1 the substance of the lungs. This membrane
is calléd by Cuvier the^membrctnd tympaniformis, and
upon its dilatation and ‘ contraction,: as well as the power af?
forded oT altering- the form ’ and length’ of the bronchise,
«óme of the varieties of intonation depend. The bronchise
are also slightly attached to each other, and to the oesophagus.
The muscles of the glottis, or superior larynx, are uniformly
two pair in all the birds I have examined ; but the
musclés of the inferior, or true larynx, all largely supplied
with, nerves, vary in number from one pair to five pair, according
to the genus or species,- affording a corresponding
increase in the various qualities of the yoice.
Some few birds have no true musclèè of voice at the inferior
part of their trachese. The Vultures,—some of them at
least,—are described. as being without any. No, 1 is a representation
of the lower portion of the trachea of a Vulture,
without muscles, or any true bone of divarication, the bronchial
rings almost completing the circle, with little flexibility,