1922.] *“ Renal Portal ’’ System. 101 
weaker in nitrogen than the kidney with 61 fluid in its renal 
atferent vein, and that (2) the 0°7% saline in the renal afferent 
vein caused the flow of urine from that kidney to decrease 
and ultimately to stop,' the other kidney continuing to secrete 
freely. 
Further experiments proved that the 0°7% saline solution 
in the renal afferent vein actively abstracted nitrogen from 
the arterial fluid in the intertubular plexus of that kidney, 
and thus led to the nitrogen-weaker urine. 
The data of the preceding experiments provide another 
very powerful argument in favour of the separateness of 
the renal venous meshwork from the intertubular plexus. 
Thus, to take a typical experiment, the arterial fluid was of a 
nitrogen strength of 0-000180 gm. in | c¢.c., the fluid in one 
renal afferent vein was of a nitrogen strength of 0:000326 gm., 
and the fluid in the other renal afferent vein contained no 
nitregen (pure 0°7% saline). The urine secreted by the 
kidney with the renal afferent vein fluid containing nitrogen 
was of a nitrogen strength of 0°000253 gm., and the urine 
secreted by the kidney with pure 0°7% saline in its renal 
afferent vein was of a nitrogen strength of 0:000180 gm., 
i.e. the relative nitrogen strengths of the two samples of 
rine w pelotenctnte verage relative strengths 
urine were a8 Foopigo and the a g g 
0°000193 
in six experiments were as 0000172" 
venous fluid mixes with the arterial fluid in the intertubular 
plexus, this means that three volumes of 0°7% saline are mixed 
with one volume of 0°6% saline plus 0°018°% nitrogen, an 
this should result in the kidney supplied with pure saline 
via its renal afferent vein, secreting urine at least four 
times weaker in nitrogen than the urine secreted by the 
kidney which does not have its arterial fluid diluted (in 
nitrogen) in this way but, on the contrary (according to 
the hypothesis), strengthened by admixture with the nitrogen- 
stronger renal afferent vein fluid. Thus, assuming that the 
Now if we assume that the 


' Perfusion with saline alone, even through the renal arteries, wires 
in all cases a very scanty output of ‘‘ urine.’ e 6.8 — ts 
Appendix H; Also see Experiment 4, Appendix C, in illustration of the | 
statement in the text. 
