. Comparative physiology of vertebrate respiration. Vertebrates -- Respiration; Physiology, Comparative. 88 VERTEBRATE RESPIRATION adaptation to life under these conditions. In water the insulation properties of fur are markedly reduced and in aquatic mammals are replaced functionally by blubber beneath the skin. In seals the skin temperature is only slightly above that of the surround- ing water but the visceral temperature is maintained at 37° C. Circulatory adaptations are important in aquatic homoio- therms, for the temperature of the flippers and legs may be ten degrees below the temperat
. Comparative physiology of vertebrate respiration. Vertebrates -- Respiration; Physiology, Comparative. 88 VERTEBRATE RESPIRATION adaptation to life under these conditions. In water the insulation properties of fur are markedly reduced and in aquatic mammals are replaced functionally by blubber beneath the skin. In seals the skin temperature is only slightly above that of the surround- ing water but the visceral temperature is maintained at 37° C. Circulatory adaptations are important in aquatic homoio- therms, for the temperature of the flippers and legs may be ten degrees below the temperature of the main body. This is main- tained by heat transfer across a counter-current exchange system between the afferent and efferent blood flows into the distal extremities (fig. 25). In this way the extremities continue to receive their oxygen but get less heat from the body as it would be dissipated at their surfaces. Centimetres 0 5 R. Caudal (a). Lagenorhynchus acutus -l^y'^ JJJJ^^ J^J^ >^.>_ Extremity Trunk Fig. 25. Diagrams to show (a) the juxtaposition of the afferent and efferent blood vessels to the fins and flukes of a porpoise. Each artery is sur- rounded by a multiple venous channel, (b) The counter-current mechanism ensures a conservation of heat (after Scholander, 1958).. 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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