54 DONALD D. VAN SLYKE 



normal and abnormal variations of the blood pH and bicarbonate values 

 and the changes in the acid-base balance of the body indicated by changes 

 in these values. 



The Normal Acid-Base Balance of the Body 



1. The Normal Bicarbonate Concentration of the Blood, the Plasma, 

 and Other Body Fluids. At the pH and CO 2 tension existing in the 

 blood all alkali in excess of that bound by the non-volatile acids is con- 

 verted into bicarbonate. None* can exist as free alkali (NaOH), and 

 only a negligible fraction of a per cent as normal carbonate (Na 2 CO 3 ). 



CO" 3 4.27 X 10- 11 

 From the equation jjCO' = - ^p (Seyler and Lloyd, 1917) 



one calculates that at blood reaction, H* = 4 X 10" 8 , the ratio 

 CO" 3 



NaHCO 3 ' 1000 

 Therefore, 99.9 per cent of the alkali in the blood not bound by acids other 

 than carbonic is in the form of bicarbonate. 



The concentration of the bicarbonate in the whole blood is usually 

 from 0.02 to 0.027 M, corresponding to 45 to 60 c.c. of CO 2 bound as bi- 



carbonate in 100 c.c. of blood. In the plasma it is appreciably higher, 

 0.022 to 0.031 M, or 50 to 70 volumes per cent of bicarbonate C0 2 (Van 



Slyke and Cullen, 1917). It follows that in the red cells the bicarbonate 

 concentration must be still lower than in the whole blood, and it is found to 

 be only one-half to two-thirds as great as in the plasma ( Joffe and Poulton, 

 1920). 



In the body fluids other than blood such information as we have indi- 

 cates that the bicarbonate concentration approximates that in blood plasma. 

 We have observed bicarbonate values normal for blood plasma in ascitic 

 fluid and pleural exudates, and Parsons and Shearer (1920) have observed 

 in the cerebrospinal fluid both bicarbonate and pH values normal for blood 

 plasma. Collip and Backus(a)(6) (1920) observed that the bicarbonate 

 of the spinal fluid followed that of the blood plasma when the latter was 

 altered^ although the changes in the fluid might lag some hours behind those 

 in the plasma. Palmer and Van Slyke (1918) found that absorbed bicar- 

 bonate is not retained in the blood, but is distributed to the body fluids in 

 general with approximate uniformity. 



2. The Normal Hydrogen Ion Concentration of the Blood Plasma and 

 Other Extracellular Fluids. The average normal hydrogen ion concentra- 

 tion of the blood plasma lies at or near the slightly alkaline point 

 H + =4 X 10~ 8 , or pH = 7.4. This fact was demonstrated on the basis 



