. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 644 CIRCULATION. mals, that is to say, the arterial blood returning from the lungs to the left auricle (Jig. 314, h) is directed entirely into the arteries of the system (A) from the left compartment of the ventricle (H), and the venous blood brought back to the right auricle (h1) by the vense cavae (V v*) is directed wholly into'the pul- monary vessels (P) by the right ventricular compartment ( H'). Fig. Lacerta ocellata. In all Reptiles, however, the descending aorta is formed by the union of two branches, the ri
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 644 CIRCULATION. mals, that is to say, the arterial blood returning from the lungs to the left auricle (Jig. 314, h) is directed entirely into the arteries of the system (A) from the left compartment of the ventricle (H), and the venous blood brought back to the right auricle (h1) by the vense cavae (V v*) is directed wholly into'the pul- monary vessels (P) by the right ventricular compartment ( H'). Fig. Lacerta ocellata. In all Reptiles, however, the descending aorta is formed by the union of two branches, the right and left aortic arches (Jigs. 314, 315, 316, and 317, A', A); the right corresponds with the systemic aorta of birds, and rises from the left ventricular compartment, the left arch joins the right on the back, and leads generally from the right ventricular cavity into the descending aorta. The arteries of the head and upper extremities (fg. 314, a*), arising from the right aorta (A1), which corres- ponds with the aorta of birds, and is con- nected with the left ventricular compartment, are supplied with highly arterialized blood proceeding directly from the lungs. The left arch of the aorta (A), being connected on the other hand with the right ventricular com- partment (H'), obtains, like the pulmonary artery, venous blood from the right auricle; and consequently the common trunk of the aorta, formed by the union of the right and left aortic arches, must carry to the posterior parts of the body a mixture of arterial and venous blood.* It may be remarked, however, that in the Turtle and some Lizards the left aortic arch does not join the right upon the back until after it (the left) has given off the great creliac or rather visceral artery, which supplies the whole of the alimentary canal and digestive organs with ve- nous blood (Jig. 315, I). The left aorta is thus much diminished in size before it sends its com- paratively small communicating branch to the From th
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