The biology of the amphibia (1931) (20195672539)

Title: The biology of the amphibia
Identifier: biologyofamphibi00nobl (find matches)
Year: 1931 (1930s)
Authors: Noble, Gladwyn Kingsley, 1894-1940
Subjects: Amphibians
Publisher: New York : McGraw-Hill
Contributing Library: ASC - York University Libraries
Digitizing Sponsor: York University - University of Toronto Libraries



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THE CIRCULATORY SYSTEM 191 of the spiral valve against its wall and forcing the blood received during the latter part of the contraction to flow along only the ventral surface of the valve and hence to the more ventrally situated vessels in the synangium (Fig. 73A). This blood, which comes from the ventricle last, is the oxygenated blood from the Fig. 73.—The conus arteriosus of two salamanders opened along the left side and turned back to show the valves. A. Ambystoma maculatum. B. Plethodon glutinosus. Sp.V., spiral valve. left auricle and it is directed into the carotid and systemic arches by the spiral valve. In Rana, the spiral valve completely shuts off from the pulmonary arch the systemic flow of blood; but in the salamanders, where the openings from all the arches lie in the synangium, it would seem that some mixture must occur. Never- theless, the directive action of the spiral valve is such that ink injected into the left auricle is found to be carried only to the ventral part of the truncus, from the point where the anterior arches arise. A further device for making sure that the oxygenated blood be carried to the head of Amphibia is the development of a so-called "carotid gland" at the point on the third arch where the internal and external carotids take origin. This structure is not a gland at all but merely a spongy enlargement of the arch which offers further resistance to the blood and steadies the pressure by con-
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