336 RESPIRATORY FUNCTION OF THE BLOOD 



TABLE XLIX 



100 c.c. OF Arterial Blood (CO2 tension 40 mm., Og tension 100 mm.). 



Corpuscles | | in solution . . 0-85 c.c. 



51 % by volume |- carry | of total CO2 - bound {e.o. NaHCOg) . 8 45 c.c. 



[adsorbedby Hb, etc. . 9-7 c.c. 



19 c.c. 



Plasma 



49% by volume 



^carries f of total COn 



in solution . . 1-2 c.c. 



bound (NaHCOg) . 23-8 c.c. 

 adsorbed by fibrinogen 5 c.c. 

 adsorbed by serum 



proteins. . . 1 c.c. 



31 c.c. 



100 c.c. OF Venous Blood (CO2 tension = 45 mm., 0_> tension = 40 mm.). 

 Corpuscles carry . 22 c.c. = + 3 c.c. over arterial blood. 

 Plasma carries . 34 c.c. = + 3 c.c. ,, ,, ,, 



56 c.c. + 6 c.c. ,, 



The conclusion might be drawn that some mechanism for carbon- 

 dioxide transport in the serum, quite other than that in the cells 

 involving haemoglobin, must be sought. The explanation of the 

 apparent inadequacy of the latter mechanism has been found by a 

 study of the inter-relationship between the electrolytes of serum 

 and cell contents. 



The function of serum and cell electrolytes in the transport of CO 2. 



Increase in the carbon-dioxide tension of plasma causes a re- 

 distribution of chlorides as between the blood cells and the plasma, 

 resulting in an increase in cell chloride and a decrease in plasma 

 chloride. Some carbon-dioxide also passes into the red cells. This 

 brings about a considerable increase in the electrolyte concentration 

 in the cells, and, therefore, of the osmotic pressure, and water is 

 drawn from the plasma into the cells to restore osmotic equilibrium. 

 If the consequent increase in erythrocyte volume (q.v.) is taken 

 into account, chemical analysis shows that a quantity of hydro- 

 chloric acid equivalent to the bicarbonate taken up by the plasma 

 has passed from the plasma into the cells, and the reactions 

 supposed to occur are as follows : — 



NaCl + H2CO3 = NaHCOg -f HCl. 



This is followed by the passage of the liberated HCl through 

 the cell membrane. The hydrochloric acid then reacts with the 

 salts of haemoglobin in the same way as was previously described 

 for carbonic acid, viz. 



HCl + B.Hb = BCl + H.Hb. 



