RESPIRATION IN SOUTHERN WHALES 399 



evolution at 15° C. Ox blood on the average contains per c.mm. about i-i units of enzyme as so 

 defined. 



The adult Blue w^hale blood contained 1-4 units per c.mm. 



The foetal Blue whale blood contained 0-35 unit per c.mm. i.e. about 25 per cent of the 

 mother blood. 

 The goat foetal blood had usually less than 10 per cent of the activity of the mother blood, so 

 that the whale foetus blood was relatively potent. 



SUMMARY 



1. The conditions underlying the respiratory activities of Southern Blue and Fin 

 whales were investigated in South Georgia and on board the pelagic whaler ' Southern 

 Princess '. 



2. The environment of these whales and some aspects of their aquatic existence have 

 been considered in relation to their respiratory demands and limitations. Instances of 

 deep and prolonged diving have been quoted. The inference has been drawn that unless 

 whales are different in some respects from other mammals they would be liable to 

 caisson sickness. Histological evidence suggests that whales expel as much air as pos- 

 sible at each expiration in order to compensate for the hardships of prolonged holding 

 of the breath. 



3. Gas analyses were undertaken to show the condition of urine, allantoic fluid, and 

 blood, and the possible influence on these of the whale's submarine activity. Large 

 volumes of carbon dioxide have been found dissolved in urine and allantoic fluid, which 

 indicate that high partial pressures of this gas are common within the whale. Slight 

 supersaturation of urine and allantoic fluid with nitrogen has been observed. 



Adult and foetal blood hardly ever contain as much dissolved nitrogen as is soluble 

 in the blood of other mammals at atmospheric pressure. In addition, the nitrogen 

 capacity of whale blood has been shown to be more than twice that of human blood. 

 Whale blood therefore is found with very much less nitrogen than could be dissolved 

 in it from the air in the lungs. 



Nitrogen disappears in the blood and cannot be extracted from it by evacuation. It 

 has not been possible to measure the maximum rate of disappearance of nitrogen ; the 

 greatest volume removed was 27 vol. per cent in 40 min. The disappearance of nitrogen 

 is contingent on the presence of oxygen. 



4. Small organisms, referred to provisionally as X organisms, have been observed in 

 all samples of adult and foetal blood. Their diameter varies from 0-5 to 2-o/t. They re- 

 produce rapidly in vitro and are resistant to freezing. Crude cultures of these organisms 

 were found to have the power to take up more nitrogen than should be soluble in physical 

 solution and of disposing of the nitrogen in some way so that it was not recoverable by 

 evacuation. Pig's blood infected with these organisms behaves like whale blood in dis- 

 posing of nitrogen. In the face of the evidence which has been collected it is difficult to 

 avoid the conclusion that the organisms are responsible for a kind of nitrogen " fixation " 

 and that their presence in whale blood serves to protect the whale from caisson sickness. 



