. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. THE CIRCULATION OF THE BLOOD. 105 cliannels so us to return constantly to its point of de- parture. Certain Worms (as tlie Eartli - worm) have a ventral tube, convevin<5 the blood from head to tail, with numer- ous cross canals joining the ventral and dorsal tubes. In the Lobster and Crab, Spider and Scorpion, the dorsal. Fig. 69.—Circulation iu a Lobster: a, heart; h, artery for the e3es: c, artery for an- teiiuse; d, hepatic artery; e, superior abdominal artery;/, sternal artery; i?, ve- nous sinus
. Comparative zoology, structural and systematic. For use in schools and colleges. Zoology. THE CIRCULATION OF THE BLOOD. 105 cliannels so us to return constantly to its point of de- parture. Certain Worms (as tlie Eartli - worm) have a ventral tube, convevin<5 the blood from head to tail, with numer- ous cross canals joining the ventral and dorsal tubes. In the Lobster and Crab, Spider and Scorpion, the dorsal. Fig. 69.—Circulation iu a Lobster: a, heart; h, artery for the e3es: c, artery for an- teiiuse; d, hepatic artery; e, superior abdominal artery;/, sternal artery; i?, ve- nous sinuses transmitting blood from the body to Uie brauchiaa, h, whence it returns to the heart by the branchio-cardiac vessels, i. tube sends off a system of arteries (not found in Insects); but the blood, as it leaves these tul)es, escapes into the getieral cavity, as in other Articulates. The Lobster and Crab, however, show a great advance in the concentration of the propelling power into a short muscular sac — the first rudiment of a true heart. A third development of the circulatory system is fur- nished by the MoUusks. Comparatively sluggish, they need a powerful force - pump in the form of a compact heart. In the Oyster and Snail, we find such an organ having tw^o cavities — an auricle and a ventricle, one for receiving, and the other for distributing, the blood. The auricle injects the blood into the ventricle, which propels it by countless arteries to the various organs. Thence it passes, not immediately to the veins, as in higher animals,' but into the spaces around the alimentary canal. A part of this is carried by vessels to the gills or lung, and then returned with the unpnrified portion to the auricle. The. 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 Orton, James, 1830-1877. New York, Harper
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishe, booksubjectzoology
