RESPIRATION IN SOUTHERN WHALES 



381 



body if need be, though the absorption of water isotonic with the blood from sea water 

 would entail the expenditure of energy. Under the circumstances it is probable that the 

 extra water thus excreted, whatever the reason, is withdrawn from the blood plasma 

 temporarily when the whale is under high pressure, compensation being made from the 

 sea at leisure when severe demands are not being made upon the whale's metabolic 

 resources. 



DISSOLVED CARBON DIOXIDE VOLS/. 



Fig. 2. The relation between the dissolved carbon dioxide and the 

 sah content of whale urine. 



Professor Krogh objects to this theory of carbon dioxide excretion on the ground that 

 the quantities thus disposed of would be negligible, since they would correspond at 

 most only to the volume of urine compared with the volume of the whale. It is not 

 known by what means whales are able to avoid taking up salts from their food or from 

 sea water swallowed. It is evident that a mechanism of some sort exists, so that there is 

 no reason why whales should not extract from the sea unlimited quantities of water 

 isotonic with the blood and pass it immediately through the kidneys. 



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