The effect of altitude 



257 



If the blood be thoroughly shaken the CO 2 may be shaken out. 

 With the small quantities of blood which we used (1 2 c.c.) about 

 ten minutes shaking was usually employed. Suppose now, we have 

 some blood which has been so treated. Let it be some of my own for 

 instance, it will give a certain dissociation curve : with another 

 portion of the same blood to which '01% lactic acid has been added 

 another dissociation curve will be obtained, and if '02/ lactic 

 acid be added we get yet a third curve. Now let us take a certain 

 oxygen pressure, say 17 mm. of mercury, it will be seen from an 

 inspection of Fig. 125 that at 17 mm. oxygen pressure we get 

 percentage saturations corresponding to the stated quantities of 



100 



I7MM. 



10 20 30 40 50 60 70 80 90 100 



FIG. 125. 



acid added to the blood of a particular person. We may express such 

 results graphically : if we do we get a curve such as that shown in 

 Fig. 126. This curve may then be used as the basis of determinations 

 of unknown quantities of acid added to the blood in the body of the 

 person for whom it has been determined. The blood is withdrawn from 

 the finger or the arm, the CO 2 is shaken out, it is exposed to 17 mm. 

 pressure of oxygen at 37 C. and the percentage saturation with oxygen 

 is determined ; the amount of acid is then read off from the curve. 



It is necessary, of course, to make a curve for the blood of each 

 person ; moreover, the method is only approximate, but it has the 



17 



B. R. P. 



