eS ee 
1922.] ** Renal Portal’? System, 89 
but in this case the pressure used was obtained by means of 
than usual. It was found — ep ig the single ! injection 
was made by the artery [aorta] or by the renal portal vein, 
the whole of the intertubular salary network appeared t o be 
injected.' In the case of the double injections rarterial bottle 
head of fluid = 20-24 cms. pressure, and ‘renal portal” vein 
the intertubular capillaries showed, some the arterial fluid, some 
the venous, and some a mixture of both.”’' Thus these results 
alone, imperfect as the experiments were, afford some evidence 
in favour of the view that the ‘ intertubular capillaries ”’ 
really consist of two distinct kinds of vessels (since if the 
arteries and veins opened into a common plexus, all the 
constituent “ capillaries”’ woul e filled with a purple 
mixture)—those filled with ‘ a fluid” {the intertubular 
plexus proper), those with ‘‘ venous” (the renal venous mesh- 
work) and those with “‘a mixture of both” (the distal portions 
f the renal venous meshwork into which the intertubular 
capillaries have opened). 
Conditions essential for the Conduct : trustworthy 
ye-injection Hxpervmen 
It is evident that fluid pressure in any given system of 
ot 
only on the pressure head of the fluid in that bottle but also 
on he aie of the cannula nozzle tied into the artery or 
vein and the resistance to outflow of the fluid from the system 
of blood vessels. In my early perfusion experiments on the 
frog I, like previous investigators. merely maintained the 
height of the fluid in the aortic perfusion bottle 24 cms. above 
the level of the aorta, and the height of the fluid in the renal 
afferent vein bottle 10 cms. above the level of the vein, and it 
was only when I discovered that, under these conditions, the 
relative flows of fluid through the aorta and each renal afferent 
vein respectively were very differ e flows via the renal 
afferent veins always being excessive relative to the aortic 
flow) from the flows obtaining in the al frog that it 
deration. Assuming that the maintenance of correct relative 
flows of fluid through the renal arteries and renal afferent vein 
of each kidney will ensure the maintenance of correct relative 
fluid pressures in the renal venous a ek ete a 
exus. I ascertained (see Appendix A) in five perfusion 
experiments (1) that in the normal ean frog Bone tigrina) 

1 My Italics. 
