. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. THE HEART AND ITS VESSELS. 283 from the third branchial vein (Fig. 227, 4, Ap}. The pulmonary artery therefore contains far more arterial than venous blood, and thus the lungs of the Salamander larva, like the air-bladder of Fishes, can have no important respiratory function. The internal carotid (ci) arises from the first branchial vein, towards the middle line, the external carotid (c'c) coming off further outwards. The latter, as it passes forwards, becomes connected with the first branchial
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. THE HEART AND ITS VESSELS. 283 from the third branchial vein (Fig. 227, 4, Ap}. The pulmonary artery therefore contains far more arterial than venous blood, and thus the lungs of the Salamander larva, like the air-bladder of Fishes, can have no important respiratory function. The internal carotid (ci) arises from the first branchial vein, towards the middle line, the external carotid (c'c) coming off further outwards. The latter, as it passes forwards, becomes connected with the first branchial arch (1) by net-like anastomoses (t), and these give rise later to the so-called carotid gland1 of the adult, which functions as an accessory heart. Direct connections exist between the second and third branchial arteries and the corresponding veins (see 227, a, a). t .. KJC. 227.—THE ARTERIAL OF THE LARVA OF A SALAMANDER. (Sliglitlj diagrammatic. (After J. E. V. Boas.) tr, conns arteriosns ; 1 to 3, the three liranchial arteries ; / to III, the corresponding •branchial veins ; 4> the fourth arterial arch, which becomes connected with the pulmonary artery (Ap) ; a, a, direct anastomoses between the second and third branchial arteries and branchial veins; ce, external carotid ; ci, internal carotid : t, net-like anastomoses between the external carotid and the first branchial artery, which give rise later to the carotid gland ; UA, aortic roots ; Ao, dorsal aorta. The arrows show the course which the blood takes. Towards the end of the larval period, the second branchial vein increases considerably in relative size, and the fourth arterial arch also becomes larger. By a reduction of the anastomosis with the third branchial vein, the fourth arterial arch furnishes the main amount of blood for the pulmonary artery, and the latter thus contains far more arterial than venous blood. When branchial respiration ceases, the anastomoses between the branchial arteries and v
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