1922.] “ Renal Portal’”’ System. 105 
one quarter of its volume of arterial blood! in normal animals, 
yet it is very doubtful if active glandular cells would, under 
these circumstances, obtain sufficient oxygen, since we know 
that the oxygen consumption per gram of kidney tissue is cer- 
tainly not less than in other organs; and (c) ‘‘when the same 
kidney is perfused at different times through the aorta, and 
through the renal portal system, there isa greater consump- 
tion of oxygen in the former case than in the latter (double to 
treble in four experiments)’’? (10), a fact which it is impossible to 
explain on any other theory than that the ‘‘renal portal ” sys- 
tem does not come into physiological contact with the tubules, 
since the Bowman capsules (supposed to be mere filters) cannot 
be supposed to absorb oxygen to any appreciable extent. 
s we have seen, the evidence advanced by physiologists 
in favour of the view that the renal venous meshwork and the 
intertubular plexus proper form one common system of sinu- 
soids supplying the tubules, is invalidated by the lack of 
precautions to secure correct relative rates of flow of the 
aorta, and it is most essential in double dye-injection and other 
perfusion experiments that these relative rates of flow should 
be reproduced, since if, as I contend, the intertubular plexus 
and the renal venous meshwork constitute two separate 
systems of channels (the former only opening into the latter 
at points where the blood is near the efferent renal veins). any 
departures from the normal relative rates of flow will cause 
either the arterial or the venous fluids to penetrate into 
channels which the blood they represent in the living animal 
never enters. J have referred to numerous perfusion experi- 
ments conducted by me, the results of which prove that under 
v 
normal conditions the fluid in the renal venous meshwork has 
also, the venous blood in the renal venous meshwork, under 
normal conditions, does not affect the kidney secretion. Under 

re 15. I need hardly say that there is no justification for either of 
these colors. The blood in the renal afferent veins is as blue as that in 
the post-caval. 
| It may also be recalled to mind that, owing to the heart of the frog 
only possessing a single ventricle, the blood in the aorta is not purely 
arterial as in higher Vertebrates but is already mixed to some extent 
with venous blood. 
2 The smal] amount of oxygen which is absorbed on perfusion via the 
**renal portal’? sys is probably due to the fluid penetrating into 
part of the empty intertubular capillary plexus, 
