178 



Chapter XI 



hold is taken, i.e that the blood is reduced from 94 per cent, to 

 44 per cent, saturation. The blackened portion of the curve of 

 oxidation was to represent that portion of the curve which is involved 

 in the actual oxidation of the venous blood. 



Fresh difficulties assailed me when I endeavoured to apply the 

 same sort of process to Oinuma's curve of reduction Fig. 93 c. In the 

 first place was it justifiable to make use of this curve ? It involves 

 the assumption that the oxygen pressure in the tissue is nil. Verzar's 

 investigations were undertaken for the purpose of testing this as- 

 sumption. It proved to be incorrect for resting organs generally. 

 The oxygen pressure in the tissue, like the percentage saturation 

 of the blood leaving it, might be anything below a certain maximum. 



100 



80 



60 



40 



20 



\ 



L 



\ 



\ 



10 20 30 40 50 60 

 FIG. 94. 



10 



20 30 

 FIG. 95. 



40 



50 



FIGS. 94 and 95. Bates of oxidation and reduction of blood. Temp. 37 C. Ordinate = 

 percentage saturation with oxygen. Abscissa = time in minutes. Fig. 94. Upper 

 curve, reducing gas nitrogen + 27 mm. oxygen + 40 mm. C0 2 . Lower curve, 

 nitrogen + 40 mm. C0 2 . Fig. 95. Keduction curves as in Fig. 94, oxidising gas 

 nitrogen + 100 mm. oxygen + 40 mm. C0 2 . 



We imagined a case in which it is 27 mm.* Fresh determinations 

 were made by Nikiferowski and I for the purpose of relating the 

 curves of reduction of blood in the presence of mm. O 2 and of 

 27 mm. O 2 respectively. The result is given in Fig. 94. The 27 mm. 

 curve of course came to a different base line from the mm. curve, 

 inasmuch as blood in presence of 27 mm. oxygen comes to an 

 equilibrium at about 40 per cent, saturation. 



Here then was my base line for the 27 mm. curve. It is the 

 upper reduction curve in Figs. 94 and 95. It now remained to be 

 blackened between the points of 94 and 44 per cent, saturation to 

 arrive at the portion involved in the reduction. 



* See p. 169. 



