FUNCTIONS OF BLOOD 113 



tion. During the heaviest sustained work in young athletic 

 men, involving an oxygen consumption of 4 1/m, it may reach 

 the astonishing figure of 35 1/m with an oxygen unsaturation 

 in the venous blood of 120 ml/1 or 70% of the arterial sat- 

 uration (E. H. Christensen, 1931). This means that in the 

 venous blood from the active muscles the oxygen concentra- 

 tion must be definitely lower than 50 ml/1. Corresponding 

 figures are not available for any other organism. The influ- 

 ence of activity upon the local and general circulation in sgme 

 lower forms both vertebrate and invertebrate would be well 

 worth studying. 



