482 VETERINARY PHYSIOLOGY 



with other acids, such as ;8-oxybutyric, then the amount of 

 CO2 must be decreased. 



The proteins of the blood are amphoteric, and it has 



been suggested that they too may combine with COg. 



The protein of the pigment of the red cells does seem 



to form such a combination. This will be considered 

 later. 



Behind the regulation of the Cjj of the blood by 

 the NaHCOg and the lungs are two further lines of 

 defence. 



1. The dissociated HCl of the NaCi of the plasma can, 

 Avhen the Cg of the blood increases, pass into the cells and, 

 seizing upon some of the sodium of the NajHPO^ turn out 

 NaHoP04 into the plasma to be excreted by the kidneys. 

 Thus some of the excess H ions is got rid of. 



Plasma 



H2CO3 + NaCl^NaHCOs + HCI 



Cell Wall 



Cell 



HCl + Na.HPO^^XaH.PO, + NaCl 



I 

 Plasma 



In fact, the kidneys play a part only second to the lungs 

 in regulating the Cr of the blood by getting rid of any 

 excess of H ions in acidosis and of OH ions in alkalosis. 



2. With any increase of the H ions and the development 

 of acidosis, the ammonia, which is in the liver normally 

 converted into urea, is passed into the blood to unite with 

 and neutralise the acids (p. 360). 



