The call for oxygen considered as a physiological test 109 



In the experiment which I have quoted a number of changes 

 took place in the vascular conditions, any one of which might easily 

 have had an effect on the flow of urine, all of which may have con- 

 spired in this matter. There was for instance an increase in the 

 general arterial pressure, an increase in the rate of flow, a decrease 

 in the viscosity of the blood and a decrease in the concentration of 

 proteins in the plasma. We can proceed to eliminate these one by 

 one and see whether a diuresis follows, a diuresis which preserves its 

 characteristic feature of taking place without any call for oxygen. 



OH 



Girpuscfe Blood 



I I 



Corpusde 



FIG. 62. Rabbit. FIG. 63. Rabbit. 



Oxygen and urine plotted as in Fig. 60. 



The change in the blood-flow and the general arterial pressure 

 may be eliminated together. 



The method of performing the experiment which is least up- 

 setting in every way is to suspend, in the Ringer's solution, red blood 

 corpuscles, then to remove a certain quantity of blood and replace it 

 by the suspension of corpuscles. If this is done, one gets a very 

 considerable diuresis, the vascular conditions of the kidney remain 

 practically unaltered, the composition of the blood remains unaltered 

 as regards salts, and there is no tendency to anaemia. One factor only 

 has been introduced, the plasma is less concentrated in protein : yet 

 a copious flow of urine is at once set up ; the question faces one, 



