224 



Chapter XIV 



Cambridge, Feb. 1910, C0 2 40 mm. 

 Teneriffe, March 1910, C0 2 40 mm. 

 Cambridge, May 1910, CO S 40 mm. 

 Pisa, August 1911, CO 2 40 mm. 



Data for my curve similar to those given for Douglas' in Fig. 106 

 are shown in Fig. 107. Similar curves might be given for other 

 observers, but I will only burden the reader with one more, namely 

 that of Higgins. His has a special interest inasmuch as it is the one 

 recorded case of the curve in a normal person changing to an extent 

 that is appreciable. The determinations were made (l)in Cambridge 

 in January 1911 by myself, (2) in Boston (Mass.), in September of 

 the same year by Higgins himself, and (3) in November 1912, also by 

 Higgins, at Boston. The first two sets of observations fall upon the 

 same curve, the last falls upon a slightly different one. These two 

 curves are shown with the corresponding observations as 1 and 2 in 

 Fig. 108, whilst the two are shown together in the lower part of the 

 figure in order that the reader may judge of the disparity between 

 the two. It will be seen that the difference between the two curves 

 is very small. This is the greatest difference discovered in any one 

 person under normal conditions. 



Let me turn to the differences which may be observed between 

 the curves of different individuals. The reader will remember that 



ii Kx n 



any one of these curves is represented by the equation -^ = yri? ~ n 



where y is the percentage saturation with oxygen, x the oxygen 

 pressure, K the equilibrium constant, and n the average number of 

 molecules of haemoglobin aggregated together. The simplest way of 

 presenting these curves will be to give the values of K in each case, 

 n being in all cases 2*5. The following is the result, the curves being 

 taken in order from the greatest to the smallest value of K. 



