Aggregation theory 



65 



above. The amount of CO 2 present has been in each case that 

 present in the alveolar air. We arrive at a very interesting result, 

 however, by studying the curves of the same blood with different 

 quantities of carbonic acid. In a couple of words it is this : the 

 equations for all such curves seem to* differ from one another in 

 the value of K only, n remaining constant for the series. This is but 

 another way of saying that the series consists of a single curve drawn 

 to different horizontal scales and can be derived from the statement 

 that the effect of the CO* is to lessen the effective concentration 



of oxygen. 



100i 



90 100 



10 20 30 40 00 GO 70 80 



FIG. 34. Dissociation curves of Barcroft's blood. Exposed to 0, 3, 20, 40 and 90 mm. C0 2 . 

 Ordinate = percentage saturation. Abscissa = oxygen pressure. 



In Fig. 34 n is 2*5 and the values of K for the various CO 2 

 pressures concerned are 



CO, pressure in mm 3 20 40 90 



K -00258 -00130 -000505 -000292 -000135 



The fact that n remains constant throughout the whole series of 

 curves places the theory under discussion upon a wholly different 

 stratum of probability. 



Up to this point we have considered K and n as being merely 

 mathematical constants though it is true they were arrived at by a 

 physical process of reasoning ; all that we have claimed for them is 

 that by suitably changing them we can reproduce the curves obtained 

 by analysis. Now however we are face to face with the fact that one 



* See Appendix II. 



B. R. F. 5 



