336 CO, Capacity of Blood. I 
Blood Plasma. Respiration. 
CO:2 in form of Pulmonary ven- wi 
Ca CO: tilation in ce. Condition. 
aoe in alveolar | of ah. 5.5 
2COs air, ec. COz elimi- 
H2CO3+ NaHCOs NaHCoz nated. 
vol. per cent ee bee per cent CG. 
63 3:60 | Normal.| 5.4 100 Normal level of 
COz: alkali. 
42 2: 40 3.6 150 Low level of CO: 
. alkali. 
84 4:80 H ine 75 High level of 
CO,: alkali. 
The expression ‘‘level of CO, and alkali” does not mean the pro- 
portion of CO, to alkali but the quantity of both; that is, their sum. 
Thus when in the plasma the proportion of H,CO3;:NaHCQO; is 
3:60 the level of the equilibrium (C,,) is normal or nearly normal 
at 63. When it is 2:40 the equilibrium is at the low level of 42, 
while 4:80 is at the high level of 84. In all these cases the pro- 
portion of H,CO;:NaHCO; is equal to 1:20 and the C, may (theo- 
retically) be the same; that is, normal (Van Slyke and Cullen‘). 
The breathing to maintain this equilibrium must, for a definite 
CO, elimination, be 50 per cent greater than normal at the low 
level and 25 per cent less than normal at the high level. When- 
ever the proportion is forced away from 1:20 (or its equivalents 
in respect to C, 3:60, 4:80, 2:40) the system seeks by physiologi- 
cal means to reattain equilibrium, in as nearly the normal C, as 
possible, at a new level. If the proportion is more than 1:20 the 
C,, 1s above normal and if less than 1:20 it is below normal (cf. 
Peters).? 
These figures apply to plasma, in which, at least for theoretical 
discussion, the conditions are comparatively simple. For whole 
blood these figures should be somewhat smaller (about five- 
sixths). For the purposes of our experiments analyses of plasma 
would however be much less significant than whole blood. 
In the production and maintenance of the low level as it exists 
probably in acidosis of renal or metabolic origin the alkali of the 
‘Van Slyke, D. D., and Cullen, G. E., J. Biol. Chem., 1917, xxx, 294. 
