Rates of oxidation and reduction of blood 181 



which it had previously reduced the blood from 95 to 45 per cent, 

 saturation. Now the corpuscle goes back to the lung where it has 

 to be oxidised from 35 to 85 per cent, to complete the cycle. 

 This process can take place within the time allotted, namely one 

 quarter of the period which the blood formerly spent in the lung in 

 which the leisurely oxidation from 45 to 95 per cent, had previously 

 taken place. This cycle is represented in Fig. 96 c. The difference 

 then between Figs. 96 A and 96 c are as follows : firstly as regards 

 the assumptions made, in the first case the " high and low water " 

 marks for oxygen are 95 and 45 per cent, and the pressure in the 

 oxygen tissue is 27 mm. In the second case the marks are 85 and 

 35 per cent, saturation and the oxygen pressure in the tissue is nil. 

 These alterations in the assumed conditions provide for a four-fold 

 increase in the rate at which the haemoglobin can acquire and expel 

 a given quantity of oxygen. 



There is a certain amount of evidence in favour of the view that 

 the arterial blood is slightly less oxidised during activity than during 

 rest. The experiments most to the point are those of Hill and 

 Nabarro <3) . The average of their normal animals gave 17'44 as being 

 the oxygen in the arterial blood (15 animals). During the tonic 

 phase of fits induced by absinthe the average was 16'11, whilst in 

 the clonic phase 17 '21. The subject is one which might suitably be 

 reinvestigated with due precautions to ascertain the percentage satura- 

 tion in each case and to ensure that there was efficient oxygenation 

 in all phases of the experiment. 



REFERENCES 



(1) Oinuma, Journal of Physiol. XLIII, p. 364, 1911. 



(2) Barcroft and Cooke, Ibid. XLVII; Proc. of Physiol. Soc. Dec. 1913. 



(3) Hill and Nabarro, Journal of Physiol. xvm, p. 218, 1895. 



