The laws and mechanics of circulation, with the principle involved in animal movement . sus; B, the three upper pairs of branchial arteries; P, P, the lower pairproceeding to the lungs or pulmonic arteries ; b, branchial veins ; v, pulmonary veins ;V, vena cava ; I, hepatic vein ; H, ventricle of the heart, surmounted by the largeright auricle. as in Menobranchus, is entire. The ventricle is of a flattened,triangular form ; its cavity is occupied by the loose, fasciculatemuscular structure, through which the blood filters, as througha sponge, from the small contiguous auricular apertures, each
The laws and mechanics of circulation, with the principle involved in animal movement . sus; B, the three upper pairs of branchial arteries; P, P, the lower pairproceeding to the lungs or pulmonic arteries ; b, branchial veins ; v, pulmonary veins ;V, vena cava ; I, hepatic vein ; H, ventricle of the heart, surmounted by the largeright auricle. as in Menobranchus, is entire. The ventricle is of a flattened,triangular form ; its cavity is occupied by the loose, fasciculatemuscular structure, through which the blood filters, as througha sponge, from the small contiguous auricular apertures, eachof which has a simple valve, to the ostium arteriosum. * Owen, Fig. 333. DIFFERENTIATION- OF LEFT AURICLE. 413 The artery inclines, with a slight twist, to the left, and swellsinto a spherical bulb. The valves are confined to the narrowerpart, and are in two transverse rows, four in each row, eachvalve of a conical shape, pointing forward.* The first row isjust above the ostium ; the second is half-way between thisand the bulb. The pulmonic auricle augments in size with the more ex-. Fig. 170.—Respiratory and Circulatory Organs in the Frog, showing increase inpulmonic and cardiac development.—Williams, a, Vena cava ; 6, right auricle ;c, pulmonary veins ; d, sinus ; i, left auricle ; e, ventricle ; /, Truncus arteriosus ;g, right carotid artery ; k, left carotid ; h, vessel to anterior extremity I, vessels tomandibular region and face ; m, abdominal aorta, formed by the junction of thetwo aortse. elusive share taken by the lungs in respiration; but theauricular part of the heart shows hardly any outward sign ofits division in batrachians. It is small, smooth, and situ-ated to the left, and in advance of the ventricle, in newts andsalamanders (Fig. 171). In frogs and toads, the auricle is applied to the base of theventricle, and to the back and side of the aorta and its ventricle, usually of a more rounded form, is occupied by * Catalogue of the Physiological Series
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