332 



Comparative Animal Physiology 



6. In the cells most buffering is provided by phosphate and hemoglobin 



K2HP04+H + :;=^KH2P04+K+ 

 BHb+H + ::^HHb+B + 



7. Deoxygenated Hb is a weaker acid than oxy Hb; hence as Oo is given off 

 in the tissues more cations (B+) are freed, and in the lungs as CO2 is lost the 

 stronger oxy Hb attracts more base, thus freeing more COo. 



8. Some COo (5-10 per cent of the total in the blood) combines reversibly 

 with hemoglobin as a carbamino compound called carbhemoglobin. 



pH 



Fig. 85. Titration curves of bloods of man, Lintiilus, and Echinus. 

 Data assembled by Barcroft.' 



CO^ Transport in Lower Vertebrates. Buffering capacity of vertebrate 

 blood is provided by the bicarbonatcs, phosphates, the plasma proteins, and 

 hemoglobin. Ihe relative importance of each kind of buffer varies among 



