. Comparative physiology of vertebrate respiration. Vertebrates -- Respiration; Physiology, Comparative. THE HEART AND CIRCULATORY SYSTEM 123 saturation of the blood in the carotid artery is lowered by 10- 20%, which indicates to what extent the patency of the ductus arteriosus compensates for the relative inefficiency of the respiratory exchange. Occlusion of the ductus arteriosus nor- mally takes place by differential growth and its constriction is complete within a day of birth, but it already begins one-quarter of an hour after the dehvery of the new-born lamb. In other mammals its complet
. Comparative physiology of vertebrate respiration. Vertebrates -- Respiration; Physiology, Comparative. THE HEART AND CIRCULATORY SYSTEM 123 saturation of the blood in the carotid artery is lowered by 10- 20%, which indicates to what extent the patency of the ductus arteriosus compensates for the relative inefficiency of the respiratory exchange. Occlusion of the ductus arteriosus nor- mally takes place by differential growth and its constriction is complete within a day of birth, but it already begins one-quarter of an hour after the dehvery of the new-born lamb. In other mammals its complete occlusion may take a much longer period,. FOETAL [body] I | DA -0- |r heart I NEONATAL iW] |l heart [ ADULT Fig. 37. Diagrams of the changes in circulation which occur at birth of a lamb (from Born, Dawes, Mott, and Widdicombe, 1954). notably some aquatic mammals such as seals and whales where it may be patent for as long as 20 days after birth. The knowledge obtained about this circulation during the change from an incomplete to a complete double circulation. 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 Hughes, G. M. (George Morgan). Cambridge, Mass. , Harvard University Press
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