Effect of acid on dissociation curve 55 



of lactic acid to '2 / as by exposing the blood to 100 % CO.,, a change 

 which in each case increases the hydrogen ion concentration of the 

 plasma from lO" 75 to lO" 4 ' 5 . 



Similarly, blood made up with lactic acid to M/120 has about the 

 same affinity for oxygen as blood made up to M/130 with hydrochloric 

 acid, and so forth. 



The affinities of the samples of blood for oxygen were not com- 

 pared in these cases by means of the dissociation curve, but by another 

 method, that of bubbling a uniform stream of nitrogen through the 

 blood and testing the rate at which it became reduced, i.e. the time 

 taken to attain a given degree of reduction. Allusion has already 

 been made to this procedure. The method was adapted somewhat 

 for the purpose by Mathison (3) , who performed the experiments with 

 which I am now dealing. It is described in Chapter XI. Here I am 

 discussing the results. 



This method no doubt expresses dynamically the facts concerning 

 the relation of haemoglobin to oxygen, just as they are expressed 

 statically by the dissociation curve. It is very desirable however that 

 actual determinations should be carried out in which the hydrogen ion 

 estimations are measured with the gas chain battery, and the affinity 

 of the haemoglobin for oxygen by means of the dissociation curve. 

 This is a very difficult matter, but the work which has recently been 

 published from Hasselbalch's (4) laboratory offers a bright promise in 

 this respect. 



In the meantime, let me give as examples the data of the two 

 cases I have mentioned. From them it will be seen (1) that the 

 addition of acids greatly accelerates the reduction of the blood; 

 (2) that the concentrations of the acids necessary to produce ap- 

 proximately equal effects are those in which they produce equal 

 increments in the hydrogen ion concentration. 



From Fig. 27 it will be seen that the times taken, by blood contain- 

 ing *2 / lactic acid, to be reduced by nitrogen, and by blood without 

 lactic acid to be reduced by 100% CO 2 , are indistinguishable, and are 

 about one-tenth as great as the times necessary for the same reduction 

 without the acids; i.e. the blood is reduced from 100 / saturation to 

 80 / saturation, in about 2 minutes with the acids present, and about 

 22 minutes with the acids absent. 



From Fig. 28 it will be seen that normal blood is reduced under 

 the conditions of the experiment (in which the bubbling was more 

 rapid and the temperature higher than in the preceding one) from 



