. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. PISCES. 991 deucy towards the amphibious type, we find at the same time that the branchial as well as the osseous system manifests a most interest- ing transitional structure between the plagios- tomous and osseous fishes. We have next to consider that part of the respiratory system which is organized for breathing immediately the atmospheric air, or the lungs ; for I do not know how otherwise to designate, according either to their physiological or morphological relations, those organs which in the technical language of
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. PISCES. 991 deucy towards the amphibious type, we find at the same time that the branchial as well as the osseous system manifests a most interest- ing transitional structure between the plagios- tomous and osseous fishes. We have next to consider that part of the respiratory system which is organized for breathing immediately the atmospheric air, or the lungs ; for I do not know how otherwise to designate, according either to their physiological or morphological relations, those organs which in the technical language of the ichthyologist would be termed the swimming or air-bladder. The trachea, or to use the same technical and partial nomenclature, the " ductus pneumaticus," is a wide short membranous tube, as in the Perennibranchiate Reptiles. The glottis (fig. 524, c,) opens near the posterior part of a long rudimental thyroid cartilage (f): a few lines posterior to the isthmus faucium the opposite end of the trachea dilates into a membranous sac, which commu- nicates by two large lateral apertures with the lungs. These are widest at their anterior extre- mities, and gradually decrease in diameter to the cloaca, behind which they terminate each Fig. Respiratory and circulatory apparatus of Lepidosiren annectens, after Owen. a, auricle ; b. ventricle laid open to show the ter- mination of the vena pulmonalis, in which a black bristle is placed ; c, bulbus arteriosus laid open ; d, pericardium ; e, vena cava abdomi- nalis; f, vena pulmonalis; 1, 2, 3, 4, 5, 6, branchial arteries of left side; m, pulmonary artery ; n, pulmonary vein. in an obtuse point (fig. 525). They are lodged in the dorsal angle of the abdominal cavity behind the kidneys, and are attached by cellular tissue to all the surrounding parts, and especially to the ribs, of which they bear the impressions on their posterior surface. The an- terior part of each lung is divided into four or five small lobes, behind
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