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ccntration was 1.670 milliOsniols/ 

 liter. The effect of such a diet, which 

 is isoosmotic with sea water, is un- 

 known. 



The P50, the partial pressure (mm 

 Hg) of oxygen at which hemoglobin is 

 50 percent saturated, is a measure of 

 the blood's affinity for oxygen — the 

 higher the P-m. the lower the affinity. 

 The P50 for Gigi was 36.5 mm Hg and 

 is the highest reported for any 

 cetacean. In a list of fifty mammalian 

 species in which the ^50 has been deter- 

 mined, only four animals exhibited a 

 higher P50 (Bartels, 1971). 



Horvath et al. (1968) compared the 

 dissociation curves of several small 

 cetacea and found that a shift to the 

 left, or increased affinity for oxygen, 

 relates to individual species behavior 

 and feeding habits. Apparently this 

 pattern does not hold for the larger 

 cetaceans. 



In looking at such parameters as 

 hematocrit, oxygen capacity, and par- 

 ticularly the P^o- a pattern emerges 

 and one is tempted to ascribe this to 

 some behavioral characteristic of the 

 animal. However, one should proceed 

 with caution. 



Oxygen dissociation curves are de- 

 termined by several methods. The 

 method used by Horvath et al. ( l'^^68) 

 was to treat the blood with varying 

 levels of oxygen and sufficient CO2 

 to maintain a pH of 7.4. I, enfant ( 1969) 

 and .Schmidt-Neilsen and Larimer 

 (1958) maintained a PcO'? '^'f -*•' rnm 

 Hg in determination of their curves. 

 ■Schmidt-Neilsen and Larimer (1958) 

 observed that In terrestrial animals 

 the blood of the larger animals has 

 the higher affinity for oxygen (low 

 P.w). Lenfant (1969) pointed out that 

 this does not hold for marine mammals 

 and the calculated Pcm's using their 

 formula supports this. 



.Steen (1971) has pointed out that a 

 Pco2 ''' "^0 "I'll Hg may not repre- 

 sent the true arterial Pcoo '-^^ ^^'^ 

 animal, e.g., a cat is about 28 mm Hg. 

 .Since the ^002 ^^as a profound effect 

 on the Pm and the magnitude of the 

 Bohr shift, one is hard put to make 

 meanlnglul comparisons in marine 



30 



