. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Heart &. h—Vitelline Vein Dorsal Aorta Vitelline Artery Fig. 300. Diagrams illustrating the arrangement of the primitive heart and aortic arches, a, early stage; b, later stage. (After Heisler.) In amphioxus the ventral aorta, or the main blood vessel anterior to the liver diverticulum (Fig. 277), is connected with the dorsal aorta by a num- ber of pairs of lateral loops that encircle the anterior part of the digestive tube. There may be as many as six
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Heart &. h—Vitelline Vein Dorsal Aorta Vitelline Artery Fig. 300. Diagrams illustrating the arrangement of the primitive heart and aortic arches, a, early stage; b, later stage. (After Heisler.) In amphioxus the ventral aorta, or the main blood vessel anterior to the liver diverticulum (Fig. 277), is connected with the dorsal aorta by a num- ber of pairs of lateral loops that encircle the anterior part of the digestive tube. There may be as many as sixty pairs of these loops in the adult ani- mal, occupying a large portion of the anterior part of the body. Each pair is interrupted by the insertion of gill capillaries in which the blood takes on oxygen from the surrounding water. In true vertebrates the number of pairs of branchial loops, although less in the adult, is typically six during embryonic development, with the ex- ception of certain primitive sharks, for example Hexanchus which has seven, and some cyclostomes which exceed the typical number. The first pair is laid down as part of the original vitelline circulation (Fig. 287). Subsequently five additional pairs are laid down one after the other, be- ginning with the most anterior one (Fig. 300).. 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 Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
