. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 626 ANATOMY OF VERTEBRATES. Draiichial circulatinn ; IniTal Newt {Triton). and activity, the principal circulating vessels present the arrange- ment shown in fig. 435. The vessel, ib. 4, originally distinct and large before the deve- lopement of the gills, is now very small, and so close to the origin of 3 as to appear to be its first branch: it anastomoses with the branch 21 from the aortal root of its own side, and proceeds to the nascent lung 19. The artery 3 supplies the hind- most gill, and distri-
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. 626 ANATOMY OF VERTEBRATES. Draiichial circulatinn ; IniTal Newt {Triton). and activity, the principal circulating vessels present the arrange- ment shown in fig. 435. The vessel, ib. 4, originally distinct and large before the deve- lopement of the gills, is now very small, and so close to the origin of 3 as to appear to be its first branch: it anastomoses with the branch 21 from the aortal root of its own side, and proceeds to the nascent lung 19. The artery 3 supplies the hind- most gill, and distri- butes its branches to the several branchial leaflets, 5, where they are resolved into the capil- lary network, fig. 343, ji. 514 ; the blood is re- turned by the branchial veins, fig. 435, 7,8, to the trunk 9, which at 16 joins the corresponding vein of the middle gill to form the aortal root or arch of that side : this receives the anastomosing vessel 13, from the branchial vein of the first gill, and then sends off the accessory origin, 21, of the pulmonary artery, 1 n. The third primary vascular arch, 2, is the branchial artery of tlie middle gill: it effects a small anastomotic communication, 14, with the vein of the gill before proceeding to expend itself upon the branchial lamella;, c ; the returning trunk, 9, after receiving the anastomotic twig, 14, joins the vein, 16, of the third gill to form the aortic arch. The foremost primary vascular arch, i, before going to the first gill, anastomoses by a small channel, 5, with the vein, 9, of that gill; which vein, after the above anastomosis, sends off the vessel 11 to the head: before the anastomosis it passes back and di^â idcs into the vessel 13, joining the beginning of the aortal arch, and the recurrent branch 12, which also conveys arterialised blood to the head. As absorption of the branchia3 proceeds in the jn'ogressing metamorphosis, the following changes are observed in the above described vessels, fig. 43G : the
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