98 Journal of the Asiatic Society of Bengal. [N.S., XVIII. 
t 
to the excess of pressure in the renal afferent vein, and 
therefore renal venous meshwork, causing the venous fluid 
to penetrate to some extent into the intertubular plexus 
via the openings of the latter into the meshwork and so lead- 
ing to admixture of the venous fluid with the arterial. This 
supposition, besides being the only possible one to account for 
the facts, is confirmed by the results of dye-injection experi- 
ments carried out with excess pressure in the renal afferent 
veins—the dye can be seen to have penetrated into the inter- 
tubular plexus under these conditions. Another result of ex-— 
cess of pressure in the renal venous meshwork fluid, which I 
may mention here, is that the arterial flow is retarded, and if the 
renal afferent vein pressure be raised to about 20 cms. the arterial 
flow is stopped altogether. 
e case of indigo-carmine injected into the renal after- 
ent vein and appearing in the urine, the intensity of colour of 
the urine is, so far as I have ascertained, directly proportional 
to the amount of excess of fluid pressure in the vein, but the 
proportion is not a simple one—the urine increases in intensity 
of colour at a greater rate than the excess of pressure in the 
vein. This is possibly due to the dye behaving like common 
salt, the percentage of which in the urine is directly propor- 
tional to the fluid pressure in the intertubular plexus (vide 
sure in the intertubular plexus diminishes the percentage of 
nitrogen in the urine (vide Part III) and the percentage of nitro- 
gen found in the urine in these experiments is the balance struck 
between the increased percentage due to admixture of the ven- 
ous and arterial fluids and the diminished percentage due to 
the increase of pressure of the fluid in the intertubular plexus. 
it be argued that these facts do not constitute evidence 
for the venous fluid entering an intertubular plexus separate from 
the renal venous meshwork, because it may just as well be 
supposed that the excess of pressure in the renal afferent vein 


