Res'piratory Functions of Body Fluids 



315 



TABLE 56. EFFECT OF CO> OR DECREASE IN pH ON THE O. TENSION FOR 

 HALF SATURATION OF BLOOD IN SEVERAL GROUPS OF ANIMALS 



* Extrapolated values. 



affinities, the ti/^ sat for the loggerhead turtle being 12.0 mm. Hg (Table 



The properties of the respiratory pigments of Iish are important in limiting 

 their distribution. In Tables 55 and 56 are shown loading and unloading 

 tensions (t^at and ti/2 sat) for several different species. Fish such as the trout, 

 which live in regions of high oxygen, require higher oxygen tensions for satura- 

 tion than do such fish as the catfish and carp, whose hemoglobin loads and 

 unloads at low oxygen tensions. Table 55 shows that the oxygen capacity of 

 these different species is similar, despite marked differences in the position of 

 their O2 dissociation curves.^** 



The effect of COj in decreasing the affinity of hemoglobin for oxygen tends 



