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the only known instance in the feathered race of a species in which the receptacular
part of the lungs is not continued into the abdomen ; yet the Struthious type is strictly
preserved, and the course of development has only been restricted, not changed.

The lungs, in fact, present all the peculiarities which characterize the class of Birds.
they are fixed to the posterior part of the chest, and imbedded in the interspaces of the
ribs, presenting a free anterior surface, slightly concave, extended on a plane nearly
parallel with the axis of the trunk, and perforated by large apertures, through which the
air passes from the bronchial tubes into the air-cells.

Each lung (Pl. V figg.4. & 5.) presents an irregular sub-compressed trihedral figure,
broader anteriorly, and gradually contracted towards the posterior extremity, which is
thin and rounded off : it is smooth and concave below ; smooth and convex above, and
outwardly ; deeply indented along the upper or dorsal angle with six notches ; the inter-
mediate portions occupying the inerspaces included between the second and the ninth
ribs, and each sending off a small process. In the number of these posterior processes
or lobes the Apteryx resembles the Emeu : in the Cassowary there are eight lobes ; in the
Ostrich and Rhea there are only five lobes in each lung.

The bronchial divisions of the trachea enter the lungs about one-fifth of their length
from the anterior end, and almost immediately divide into four principal branches ; one,
a small branch (a, fig. 5.) is lost in the substance of the anterior part of the lung ; a
second, the largest branch (b, fig. 5.) , runs down the concave surface, near to and par-
arallel with the dorsal margin, and supplies the rest of the respiratory portion of the lung ;
the third branch, which is small, perforates the anterior part of the lung, and opens
into the anterior air-cell ; the fourth branch (c, fig. 5.) runs down the middle of the
concave surface of the lung, and terminates by the three successive orifices in the three in-
ferior air-cells. the inner surface of this bronchial tube presents a great contrast with
that of the second, which runs parallel with it, in the paucity of the foramina which it
presents for the passage of air into the substance of the lung ; these being extremely
numerous in the second, as shown in the figure.

The pulmonary tissue is as compact, as vascular, and presents the same peculiar spongy
texture as in other Birds. A stratum of fat was developed under the pleura, along the
anterior margin of each lung. The first or most anterior of the air-cell interposed be-
tween the lung and the diaphragm is the smallest ; the second the largest ; this and the
third present a cuboid figure : the parietes of these cells consist of an extension of the
delicate mucous membrane of the air-passages , and an external thin layer of cellular
tissue, by which they adhere to the diaphragm : the anterior air-cell on each side pro-
trudes a little way through the anterior aperture of the thorax. (See Pl. V. Fig. 4 .)

The larynx and trachea resemble, in the simplicity of their structure, those of the
other Struthious birds. the upper larynx is not defended by any rudimental epiglottis,
nor provided with retroverted spines or papilloe. The glottis (Pl. III. d, fig. 1.) is a
long and moderately wide aperture : below the external or superior lips of the glottis,