102 Journal of the Asiatic Society of Bengal. [{N.S., XVIII, 
rogen) is perfused through the renal arteries and saline plus 
nitrogen is perfused through the renal afferent veins, nitrogen 
is found to pass from the renal venous meshwork into the inter- 
tubular plexus, and the urine contains nitrogen. In other 
of substances occurs between the two systems of sinusoids in 
motic tensions evoked by the abnormal conditions permit diff- 
usion to occur. 
nother series of facts affords equally forcible evidence, 
both in favour of the separateness of the intertubular plexus 
and renal venous meshwork and of the view that it is the tu- 
bules which produce the urine and not the glomeruli. If saline 
plus nitrogen be perfused through the renal arteries, while the 
renal afferent vein is ligatured, secretion proceeds apace, but 
if pure saline be then perfused through the renal afferent vein 
with correct relative flow, the arterial flow is retarded and secre- 
tion at once becomes diminished. Apart from the abstraction 
of somenitrogen from the arterial fluid, attribute this result 
mainly to the pure saline (a fluid of relatively low osmotic pres- 
sure ) in the renal afferent vein causing constriction of the inter- 
tubular plexus capillaries. On the other hand, if a fluid of low 

| In view of the theoretical im 
: ; portance of these facts (Part IV) I have 
noe the details of a few of these experiments in Appendix C. 
Even if we assume that it can do so and that it produces an in 
creased glomerular filtrate, this filtrate will be different in composition 
y but in my experiments, wit 
one as the composition of the increased volume of urine remat 4 
*red, whatever substance was employed in the renal afferent vein fluid 
Beare als as ter Gh ee Se een a pe trent ee tie Wd os keep oe ocean 


