340 RESPIRATORY FUNCTION OF THE BLOOD 



sion, hydrogen ion concentration, free and bound carbon-dioxide, 

 r, cell volume, etc. It has, however, been shown that for any 

 given sample of blood an " alignment chart " may be drawn, and 

 graduated in such a way that each curve on it represents one 

 variable factor in the blood, and a straight line drawn to cut all the 

 curves will do so at points which give the value of each of the 

 respective factors in the blood at any one time. Hence, if the 

 simultaneous values of any two factors in the blood be known, all 

 the others may be deduced from the chart by joining the points 



\^ fv4 TotaJ CO^ COJension 



Oz HbO, 



Fifi. 83. — D'Ocagne tomogram or Aliannient Chart for the blood of A.V.B. (By courtesy 

 of L. .7. Henderson, from Ifecent Admnccs in Physiology. Kxplanation in text and also in 

 Lectures on Certain Aspects of Biochenn.itry.) 



corresponding to these values on their respective curves and 

 producing the line to intersect the other curves. 



In the alignment chart (Fig. 83) the seven graduated lines, taken 

 from left to right, represent respectively (1) the ratio, r = (anions 

 of cell)/(anions of serum) ; (2) the volume of the erythrocytes, v ; 

 (3) the total COg of the blood ; (4) the CO2 tension ; (5) the joH of 

 the serum ; (6) the oxygen tension ; and (7) the percentage satura- 

 tion of haemoglobin with oxygen. If any two of these values are 

 known for the blood for which an alignment chart has l:)een 

 constructed, then the five other concomitant values may be 

 obtained by drawing a line through the two known points. This 

 line will cut all seven lines, and the point at which it cuts a 



