. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. HEAKT OF REPTILES. 507 333. Ilearb, vascular arches, and hyo-branchlal aiiparatus, Salamander The pulmonic auricle augments in size with the more exclusive share taken by the lungs in respiration: but the auricular part of the heart shows hardly any outward sign of its division in Batrachians. It is small, smooth, and situated to the left and in advance of the ventricle, in Newts and Sala- manders, fig. 333, a. In Frogs and Toads the auricle is applied to the base of the ventricle, and to the back and side of the aorta a
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. HEAKT OF REPTILES. 507 333. Ilearb, vascular arches, and hyo-branchlal aiiparatus, Salamander The pulmonic auricle augments in size with the more exclusive share taken by the lungs in respiration: but the auricular part of the heart shows hardly any outward sign of its division in Batrachians. It is small, smooth, and situated to the left and in advance of the ventricle, in Newts and Sala- manders, fig. 333, a. In Frogs and Toads the auricle is applied to the base of the ventricle, and to the back and side of the aorta and its bulb. The ventricle, usually of a more rounded form than in fig. 331, H, is occupied by the muscular fasciculi, except at a small part between the auriculo-ven- tricular and aortal orifices. The bulbus arteriosus is incompletely divided by opjiosite longitudinal folds,the margins of which meet, but remain free. In Serpents the heart agrees with other organs in its elongate form. The auricles are in advance of the ventricle, their lower obtuse ends slightly overlapping its base : they arc sepa- rated anteriorly by the co-elongate intrapericardial origins of the arteries called ' conus arteriosus,' answering to the bulbous part in Batrachia ; a slight ' auricidar ' production of the right auricle is tied down to the arteries by the serous layer of the jjcricardium. The right auricle consists of a sinus and auricle proper. The sinus receives three veins at its fore part; the orifice of the right jugular and of the inferior azygos is guarded by a pair of valves: in the orifice of the superior azygos I found three semilunar valves; two veins o^tQn at the back or hind part of the sinus, the largest being the postcaval, the smaller one the left precaval. The aperture of communication with the auricle is longitudinal, near the middle of the sinus, of a full elliptical shape, guarded by a pair of membranous valves, situated within the proper auricle. The sinus has the structure o
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