. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 310 COMPARATIVE ANATOMY The cavity of the ventricle is unpaired, and neither in Urodela nor Anura shows any trace of a septum, so that the blood passing out from it must have a mixed character (Fig. 249). The ven- tricle is usually short and compressed, but is more elongated in Amphiuma, Proteus, and the Gymnophiona. It is continued an- teriorly into a conus arteriosus, as in Elasmobranchs, Ganoids, and Dipnoans; this has usually a slight spiral twist, and possesses a transverse row of valves at either end, as well as
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 310 COMPARATIVE ANATOMY The cavity of the ventricle is unpaired, and neither in Urodela nor Anura shows any trace of a septum, so that the blood passing out from it must have a mixed character (Fig. 249). The ven- tricle is usually short and compressed, but is more elongated in Amphiuma, Proteus, and the Gymnophiona. It is continued an- teriorly into a conus arteriosus, as in Elasmobranchs, 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 ex- tending into its This holds good for the Axolotl, Amblystoma,. Fig. 250. of Cr;/ptohra iK-lnis japonictis. From the ventral side. Rose.) Ta3 left atrium is out open. (After , septum atriorum, perforated by numerous small apertures ; ', :^, the two pulmonary veins, opening by a single aperture into the left atrium ; ; atrio-ventricular aperture ; 1", 4", the four arterial arches : , left and right pulmonary arteries ; />â , truncus arteriosus ; L. Vh, 2^. Vh, left and right atria ; and , subclavian veins ; Sund , jugular veins ; , ^, posterior cardinal veins ; , postcaval vein. Salamandra, Amphiuma, and Siren. In others (, Necturus, Proteus, Gymnophiona), 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 lyiug within the conus extends so far back that no undivided portion of the cavity is left. The consequence of this is that the blood passing into the hindermost pair of the arterial archesâthat from which the pulmonary arteries ariseâis mainly venous, while the others contain more or less mixed blood (Fig. 249, b) ; for, owing to the spongy nature of the ventricle, there 1 This spiral fold corresponds to a series of fused Please note that these imag
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
