RESPIRATION IN SOUTHERN WHALES 



379 



is placed on the line opposite the appropriate ordinate so that it is possible to read off on 

 the abscissa the partial pressure of carbon dioxide which is necessary to cause that 

 volume of gas to go into solution. The results of the control experiments are also re- 

 corded. By analogy with the behaviour of nitrogen it appears that the gas content of 

 human urine tends to be slightly above that which would be expected from an equili- 

 brium of the carbon dioxide in the alveolar air, standing constantly at 40 mm. of 

 mercury, with the blood and hence with the other body fluids. The average human 



40 



30 



in 



> 



S20- 



X 



a 



z 



o 



en 



Qi 



< 



© HUMAN CONTROLS 

 • WHALE RESULTS 



200 300 



PARTIAL PRESSURE OF CO^ [mm, HgJ 



400 



500 



Fig. I. Carbon dioxide contents of whole urine superimposed on the solubihty 

 curve of carbon dioxide in water at 36° C. 



urine gas content corresponds to a partial pressure of about 60 mm. of mercury m 

 contrast to the 40 mm. which was expected, a state of affairs which might be accounted 

 for by the diffusion direct into the urine of the carbon dioxide generated in the 

 capillaries surrounding the kidney tubules. The main point is that in comparing the 

 carbon dioxide pressures in human and whale urine a variation of 20 mm. either way 

 is of no great significance. It should be mentioned that in those cases where the com- 

 bined carbon dioxide has not been directly estimated the dissolved carbon dioxide has 

 been computed by subtracting the average combined gas, 2-20 vol. per cent, from the 



3 



D VII 



