. The chordates. Chordata. Rasic Structure f Vertebrates Asymmetry of paired blood-vessels, even the major trunks, is very common. In reptiles the chief artery of the body, the dorsal aorta, is symmetrically connected with the ventral heart by a pair of large arteries forming a so-called "aortic ; In adult birds only the right vessel of this aortic arch, complete in the embryo, persists; in mam- mals only the left vessel persists (Fig. 71). The very small arteries and \eins are quite devoid of symmetry in their arrangement. XASAL PHARYNX. Fig. 6. Diagram of the alimentary canal.
. The chordates. Chordata. Rasic Structure f Vertebrates Asymmetry of paired blood-vessels, even the major trunks, is very common. In reptiles the chief artery of the body, the dorsal aorta, is symmetrically connected with the ventral heart by a pair of large arteries forming a so-called "aortic ; In adult birds only the right vessel of this aortic arch, complete in the embryo, persists; in mam- mals only the left vessel persists (Fig. 71). The very small arteries and \eins are quite devoid of symmetry in their arrangement. XASAL PHARYNX. Fig. 6. Diagram of the alimentary canal. (Courtesy, Jackson: "Morris' Hu- man Anatomy," Philadelphia, The Blak- iston Company.) The right and left lobes of the liver and of the lungs are commonly asymmetric in number, size, form, and position. The right and left kidneys in mammals may not be exactly opposite each other. There is more or less functional modification of symmetry. In a decidedly right-handed person, the right arm and hand are more strongly de- veloped than the left. One of the most striking cases of modified symmetry is that of the "flatfishes" such as the flounder, sole, and halibut. These fishes ha- bitually rest at the bottom of the water, lying flat on one side; in some species on the right side, in others on the left. The external form of 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 Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : Blakiston
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