43

23

and within the larynx, there are two thinner membranous folds : a small but elongated
process projects from the middle line of the under or anterior part of the upper larynx,
towards the rima glottidis. Behind the glottis there are two square-shaped tumid pro-
cesses, with their free margins directed backwards into the pharynx ; their texture is
more glandular than the surrounding mucous membrane. The trachea corresponds in
length with the neck, and preserves a nearly uniform diameter throughout its course ;
it consists of small and entire cartilaginous rings, - in one specimen, 120, - in another,
130 in number, - alternatively overlapping and being overlapped at the sides when the tube
is relaxed : they are also alternately narrower on one side and the other, but in a slight
degree : they become gradually smaller to the last twenty rings, which are not connected
so closely and rigidly together as in the Ostrich and Emeu. Remembering the cervical
air-sac which projects through the ovate aperture discovered by Fremery 1 in the anterior
part of the trachea of the Emeu, and situated, as that accurate observer describes, between
the fifty-third and sixty-second cartilaginous rings, I examined with care the trachea of
the Apteryx, but without detecting any trace of an analogous structure in either sex.

There is no lower larynx. The last two tracheal rings increase in breadth, and the
bronchial rings are continued from them with only a slight diminution of thickness :
a membrane closes the trachea below, and completes the bronchial rings at their under
part : near the termination of the bronchioe the cartilaginous hoops are incomplete above
as well as below. Both circular and longitudinal muscular fibres enter into the struc-
ture of the short bronchial tubes.

The sterno-tracheales muscles (Pl.V.a,fig. 4 ; Pl. III.g fig. 3.) arise, one from the
inner surface of each coracoid bone.

It is plain, from the fixed condition of the lungs, and from the space between the lungs
and diaphragm being occupied by air-cells, that inspiration could not be effectually per-
formed by the action of the diaphragm along ; but the structure and mobility of the an-
terior parietes of the thorax indicate that it takes place in the Apteryx, as in other birds,
by the sternum being depressed, and the angle between the vertebral and sternal ribs
being increased.

All the triangular muscles which converge to be inserted into the costal processes
thus became muscles of inspiration, and more especially those which represent the ser-
ratus magnus anticus, and which act from the true ribs as a fixed point below, upon the
scapula above ; for by drawing down that bone they bear upon the sternum, through the
medium of the coracoid ; and hence the necessity of strong and well-developed coracoid
bones in a bird that otherwise could derive no particular advantage from the fixation
of the scapula. The adherence to the ornithic type in the characteristic part of the os-
seous structure due to the sternum, coracoids, and scapuloe, is thus not merely explicable

1 De Casuario Novae Hollandiae. Svo. 1819.