CELL VOLUME 341 



graduated line will gi\e the \alue for that faetor. For example, 

 ill Fig. 83, wliieli is the aliguuieut ehart for A.V.B.'s blood, if one 

 knew that, at any time, the blood, under a tension of 40 mm. Hg 

 of CO2, would give a serum with a^;!! of 7-45, then, by joining these 

 points and produeing the line to eut the other curves {i.e. the 

 line a — b in the figure) the values of r, v, total CO2, Oo 

 tension, and percentage saturation of Hb with oxygen are given 

 by the points of intersection of a — b with the respective graduated 

 curves. This shows us that when this blood has a COg tension of 

 40 mm. Hg, and its serum a p¥l of 7-45, the chlorides and biear- 

 bonates are so divided between cells and serum that [BHCOaJj 

 [BHCO3], = [C1],/[C1], = r = 0-723 ; the cell volume, v = yo\ = 

 100-1 ; the total COg = 48 per cent. ; the oxygen tension = 

 70 mm. Hg ; and the percentage saturation of haemoglobin with 

 oxygen = 92. 



A word of explanation is necessary concerning the value (vol) 

 of the cell-volume. Professor L. J. Henderson, to whom we are 

 indebted for the ehart, took the normal cell-volume (70/z") as 

 100 per cent., when the O2 tension was 80 mm. Hg and the CO2 

 tension was 39 mm. Hg. At this point the haematocrite reading 

 was 40 per cent., i.e. the cells occupied two-fifths of the total blood 

 volume and the plasma the remaining three-fifths. 



The line a — b represents a typical set of conditions for arterial 

 blood. Another line, c — d, could be drawn to represent the values 

 of the seven factors in typical venous blood. Here the COo 

 tension has risen to 47-5 mm. Hg, and the Hb saturation has fallen 

 to 65 per cent. It is evident that this produces marked alterations 

 in the values of r and v, and a less marked increase in hydrogen ion 

 concentration. Between the extremes represented by the oxygen 

 and carbon-dioxide tensions indicated by the lines a — b and c — d, 

 i.e. between arterial and venous conditions, a large number of 

 lines are possible, representing the conditions in capillary blood. 

 For example, blood with an oxygen tension of about 60 mm. Hg. 

 might pass through a very active tissue producing large quantities 

 of CO2. The blood as it reached this tissue might have the 

 following characteristics, viz. r = 0-73 ; vol. = 100-4 ; total COg 

 = 48 per cent. ; CO2 tension = 42 mm. Hg ; pH (serum) = 7-41 ; 

 and percentage Hb02 = 90 per cent. Interchanges with the active 

 tissue would cause a decrease in factors 6 and 7 on the chart, and 

 an increase in the factors represented by the first five lines, e.g. 

 r = 0-75 ; vol. = 101 ; total COg = 52-5 per cent. ; CO2 tension = 

 45 ; ^H serum = 7-42, all increase ; while Og tension = 36 mm. 

 Hg and HbOg per cent. = 70, show a decrease. Oxygen has been 

 given to the tissues, and CO2 accepted from the tissues with a 



