Respiratory Functions of Body Fluids 



313 



logically, however, after acclimatization there is a fall in alkaline reserve or 

 acid-binding material so that CO^ eflects are more marked and the tj/o sat of 

 the hemoglobin may actually increase (up to about 14,000 ft. altitude).'"' 



Table 57 also shows that the red cell count and hematocrit index of acclima- 

 tized sheep and rabbits are elevated, but in the native llama and vicuna blood 

 counts are not much different at sea level and in the mountains.'^- The oxygen 

 dissociation curves of llama and vicuna lie to the left of those of their sea level 

 relatives, and the bloods of the ostrich and huallata are also saturated at lower 

 tensions than are the bloods of other birds. Hence these native species appear 

 to have hemoglobin of high Oo affinity. Dogs reared at 14,890 feet altitude 

 have 60 to 70 per cent more myoglobin in their muscles than do dogs at sea 

 level, ■'^•'* although in dogs kept at 18,000 feet for 6 hours daily during several 

 months the hematocrit index rose by 70 per cent, but the myoglobin was 

 unchanged. ^^ 



PARTIAL PRESSURE CO. 



Fig. 70. Effects of CO2 on the O- tension tor half saturation ot blood: • man, Bock, 

 Field, and Adair''; O man, A seal, Irving et al.'''*; X fox, Irving et al.""*; -\- goose, Wastl 

 and Leiner.^'' 



Hemoglobin of Embryos. Barcroft and his associates^ found that the oxygen 

 dissociation curve of mammalian embryos is steeper than that of adults and 

 lies to the left of the normal range. The maternal curve, on the other hand, 

 lies to the right, an effect which is largely due to decreased blood pH (Fig. 75). 

 The fetal hemoglobin differs from that of the adult in loading at lower oxygen 

 tensions.'*^' '" Thus fetal hemoglobin, which is made largely in liver, resembles 

 the hemoglobin of aquatic animals more than does adult hemoglobin, which 

 is made in marrow. The embryo is adapted by its low tj/2 sat to life at lower 

 oxygen tensions. 



Similarly in incubating chickens the hemoglobin has a greater affinity for 

 oxygen than it has in the hen. The dissociation curve moves to the right after 

 hatching, and the tension for 50 per cent saturation rises. ^'^ Young birds are 



