. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 282 COMPARATIVE ANATOMY. elongated in Am phiu ma, Proteus, and the Gy mn ophiona. It is continued anteriorly into a conus arteriosus, as in Elasmo- branchs, Ganoids, and Dipnoans; this has usually a slight spiral twist, and possesses a transverse row of valves at either end, as well as a spiral fold extending into its This holds good for the Axolotl, Amblystoma, Salamandra, Amphiuma, and Siren. In others ( Menobranchus, Proteus, Gymno- ]>hiona), retrogression is seen in a lengthen
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 282 COMPARATIVE ANATOMY. elongated in Am phiu ma, Proteus, and the Gy mn ophiona. It is continued anteriorly into a conus arteriosus, as in Elasmo- branchs, Ganoids, and Dipnoans; this has usually a slight spiral twist, and possesses a transverse row of valves at either end, as well as a spiral fold extending into its This holds good for the Axolotl, Amblystoma, Salamandra, Amphiuma, and Siren. In others ( Menobranchus, Proteus, Gymno- ]>hiona), retrogression is seen in a lengthening of the conus, the disappearance of the spiral fold, and the presence of only a single row of valves. In Anura, the fold lying within the conus extends so far back that no undivided portion of the cavity is left. The conse- quence of this is that the blood in one section of the branchial. J-'K;. -22G.—DIACUAM SIIUWIM; THE CornsK OF THK THROUGH THK HEAUI IN Urodda (A) AND Anura (P>). A, right atrium; A1, left atrium; /', ventricle; tr, uonns arteriosus, divided in Anura (P>) into two portions, tr, tr1: through tr venous lilnod passes into the pulmonary arteries, Apl, Apl, while through to*1 mixed blood goes to the carotids, ci—cc, aiid to tlic roots of the aorta, KA ; h; lr, pulmonary veins ; ?•, r, pre- and postcavals (only one precaval is indieated) opening into the right atrium. vessels—that from which the pulmonary artery arises—is mainly venous, while the others contain mixed blood (Fig. 226, B); for, owing to the spongy nature of the ventricle, there is no time for its contained blood to get thoroughly mixed before it is forced into the conus. As in the Dipnoi, four branchial arteries arise on either side from the short conus in the Amphibia, which—taking as a good type the larva of Salamandra—have the following relations. The three anterior branchial arteries pass to numerous external gill-tufts, where they break up into capillaries (Fig. 22
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondonnewyorkmacmi
