. The biology of the amphibia. Amphibians. 190 THE BIOLOGY OF THE AMPHIBIA The oxygenated blood received from the lungs is squeezed from the left auricle into the left and caudal part of the ventricle. The blood that is poor in oxygen is forced from the right auricle a moment before the blood is sent from the left and tends to remain on the right side of the ventricle, being held in this posi- tion by the many muscular strands. Since the conus springs from this half of the ventricle, this poorly oxygenated blood is forced out first into the pylangium when the ventricle Fig. 72.—Hea
. The biology of the amphibia. Amphibians. 190 THE BIOLOGY OF THE AMPHIBIA The oxygenated blood received from the lungs is squeezed from the left auricle into the left and caudal part of the ventricle. The blood that is poor in oxygen is forced from the right auricle a moment before the blood is sent from the left and tends to remain on the right side of the ventricle, being held in this posi- tion by the many muscular strands. Since the conus springs from this half of the ventricle, this poorly oxygenated blood is forced out first into the pylangium when the ventricle Fig. 72.—Heart of Rana catesbeiana, frontal section, showing the septa which prevent the mixing of the arterial and venous blood in the ventricle. Ch., chorda; tendinea; , dorsal auriculo-ventricular valve; , left auricle, , left auriculo-ventricular valve; Py., pylangium; , right auricle, , right auriculo-ventricular valve; , auricular septum; Vent., ventricle. (After Benninghoff.) The blood makes its way into the nearest openings and into those vessels offering the least resistance. These are the openings into the sixth or pulmonary arches, which because of their short circuit, are free from the resistance of accumulated blood. In salamanders the openings to the pulmonary arch lie directly cephalad of the synangial valves, but in frogs the two pulmonary arches unite to form a single vessel which opens into the pylan- gium just caudal of the synangial valves. This position, nearer the source of supply, is a more favorable one for securing the first blood passed through the pylangium. As the blood is squirted into the pylangium, the latter contracts, bringing the free margin. 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 Noble, Gladwyn Kingsley, 1894-1940. New York : McGraw-Hil
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