The call for oxygen by the tissues 103 



matter before we may therefore explain more particularly what 

 we mean. 



When a gland secretes, water is taken from the blood. The result 

 is that the corpuscles in the venous blood are more numerous than 

 in the arterial blood per cubic centimetre. To find out how much 

 oxygen the blood has lost in its passage through the gland, it 

 is necessary to know the sum total of the oxygen lost by each 

 corpuscle ; therefore the amount of oxygen in the venous blood must 

 be subtracted not from the amount of oxygen in the same volume 

 of arterial blood, but from the amount of oxygen in a volume of 

 arterial blood which contains the same number of corpuscles (or the 

 same amount of haemoglobin) as are contained in the venous blood 

 collected. 



In the case of the submaxillary gland exact measurements have 

 been made. The following figure shows the relation of the volume of 

 venous blood passing through the gland during stimulation of the 

 chorda tympani, to the volume of the saliva secreted and to the 

 amount of water lost by the blood. It will be seen that the two 

 latter are almost equal in amount ; the slight excess of the water 

 lost by the blood over the saliva secreted is to be accounted for no 

 doubt as lymph (18) . To obtain the volume of arterial blood from 

 which a given volume of venous blood was derived one multiplies the 

 volume of saliva by I'l and adds it to the volume of the venous blood. 



If the conditions in the pancreas and the kidney be considered in 

 the same way, it will be found, for experiments of the order of accuracy 

 of those with which we have been dealing, that the volume of pan- 

 creatic juice or urine is so small as compared with that of the blood 

 that no correction need be introduced for the concentration. 



The following results for the oxygen used during rest and activity 

 were obtained by the ferricyanide method : 



Oxygen absorbed per min. 



Besting pancreas Active pancreas Response to injection 



Exp. 1. -49 c.c. 1-71 c.c.1 



60c.c. 3-50C.C.J g C 



Exp. 2. -25 c.c. -51 c.c.) 



34 c.c.} g d 



Exp. 3. -12 c.c. -28e.c/) 



2-1 c.c. in 8' 

 11 c.c. -34 c.c.J 



Exp. 4. -08 c.c. -33 c.c.^l 



06 c.c. -29 c.c./ 



9 c.c. in 5' 



