220 Chapter XIV 



close to fall within the six per cent, limit, and the deduction might be 

 made that there was no difference between the blood of healthy 

 persons. 



Yet another series of figures obtained by Mathison, at Pisa, on 

 the members of our Monte Rosa party, seems to indicate that the 

 blood of different persons differs. 



Ryffel 77 / 

 Eoberts 75*5 

 Camis 74 

 Barcroft 72 

 Mathison 63, 66 



These figures run slightly lower than the previous series, 

 probably because the same care was not taken to exclude C0 2 

 completely. In the former series the gas in the tonometers stood 

 over alkali before it was used, in the latter it was used as it came 

 from the cylinder. The gas contained about 1 mm. pressure of CO 2 . 

 The point is that the figures in each series are comparable with one 

 another. Clearly the differences are greater than can be accounted 

 for by experimental error. 



Having established the fundamental fact that there is a difference 

 between the blood of normal persons, apart entirely from any question 

 of the quantity of carbonic acid present, let us turn to the dis- 

 sociation curve of the blood as it leaves the lung. 



In order to gain reliable information concerning the blood of a 

 given individual it is necessary that his dissociation curve should be 

 studied over a considerable period of time, running if possible into 

 years. There are now several persons for whom this has been done, 

 Douglas, Roberts, Ryffel, Higgins and myself. The question arises with 

 regard to each of these Can any difference be made out as between 

 one time and another? This point seems to me to be of such great 

 importance that I propose to set the evidence on the subject in some 

 detail before the reader. 



Firstly then as regards Douglas whose normal alveolar carbonic 

 acid pressure is found to be 40 41 mm. of mercury. His dissocia- 

 tion curve is given in Fig. 106. Particular interest attaches to it not 

 only because it has been determined more often probably than that 

 of any other person, but because it has been determined inde- 

 pendently by two sets of observers, working by slightly different 

 methods. The points determined by me were each done on 0*1 c.c. of 

 blood in the small differential apparatus, those determined by Haldane 



