. Outlines of zoology. Zoology. CIRCULATORY SYSTEM. 489 branchial arch bears none. Each of the first four branchial arches bears a half gill on each side; thus, including the gill filaments borne on the posterior side of the hyoid, there are four and a half gills. The absence of an operculum or gill cover is obvious. The gills are outgrowths from the wall of the gut, and therefore endodermic. Circulatory System. The impure blood from the body enters the heart by a bow-shaped sinus venosus, which leads into a large thin- walled auricle. Thence through a bivalved aperture the. Fig. i5i.—Heart an
. Outlines of zoology. Zoology. CIRCULATORY SYSTEM. 489 branchial arch bears none. Each of the first four branchial arches bears a half gill on each side; thus, including the gill filaments borne on the posterior side of the hyoid, there are four and a half gills. The absence of an operculum or gill cover is obvious. The gills are outgrowths from the wall of the gut, and therefore endodermic. Circulatory System. The impure blood from the body enters the heart by a bow-shaped sinus venosus, which leads into a large thin- walled auricle. Thence through a bivalved aperture the. Fig. i5i.—Heart and adjacent vessels of Skate, after Monro.) (In part v., Ventricle; conus arteriosus; /.?'., posterior innominate; ^ ventral aorta; ^ anterior innominate; Th., thyroid; in., mouth ; a., auricle ; , sinus venosus ; , precaval sinus or sinus of Cuvler ; hepatic sinus; jugular; br., brachials; cd., car- dinal ; f/jf., epigastric. blood passes into the smaller muscular ventricle, and from this it is driven through a contractile conus arteriosus, with three longitudinal rows of five valves, into the ventral aorta. The ventral aorta gives off a pair of posterior innominate arteries, which take blood to the three posterior gills, and a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933; Newbigin, Marion I. (Marion Isabel), 1869-1934; Smith, Preserved, 1880-1941. fmo. New York, D. Appleton & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
