134 Journal of the Asiatic Society of Bengal. [N.S., XVIII, 
that (in the total absence of diuretics) the fluid in the swollen 
veins flows. This condition of things can be brought about by 
perfusing the kidney in the reverse direction to the normal, ie. 
through the renal vein or veins to the artery or arteries 
instead of vice versa. I performed five such experiments on 
the frog and four on the rabbit, the results of which are 
given in Appendix H, and they provide a sufficient disproof of 
the suggestion put forward by Ludwig, and, at the same time, 
and in conjunction with the results of Appendix G (Part ITT), 
a sufficient demonstration of the truth of the view that quanti 
-ty of urine is, other things equal, dependent on rate of flow 
and volume (i.e. on the flow) of the perfusing fluid, and that 
hydrostatic pressure in the glomerulus (except in so far as if is 
a cause of flow) and absorption in the tubules have nothing to 
o with urine production. Some rate of flow is, under most 
conditions,! absolutely essential for secretion, but the amount 
of secretion will be small or even nil unless there is also volume 
(well shown when, the renal nerves being stimulated, the renal 
capillaries contract and the urine output is diminished, though 
the blood pressure remains unaltered and the rate of low must 
be increased). 
Additional confirmation of this view is afforded by the 
familiar fact that in both the salivary gland (Starling, 40, p. 
668) and the liver (Schafer’s “‘ Text-book of Physiology,” Vol. 
I, p. 565) blood flow is the chief factor concerned in quantity of 
secretion, and not blood pressure, and the same fact doubt- 
less holds for the pancreas (27) and all other glands. In all 
these glands increased output of secretion? always, other 
conditions being the same, follows dilatation of the gland 
capillaries, and though it is sometimes assumed that this 
dilatation is solely due to a local increase of blood pressure 
(even when, as in the case of the kidney with the splanchnic 
nerve branch cut, the pressure in the artery remains constant) 
yet it seems quite as feasible to assume that the dilatation 1s 
due to relaxation of the capillary walls. the resulting lowering 
of resistance facilitating inflow of blood and thus producing 
that volume of blood which is so essential to secretion, even 
though the rate of flow be slightly reduced. 
gain, the results of the experiments described in Appen- 


_! Urine can also be produced from practically stationary bleod oF 
fluid in the intertubular plexus. provided that there be a sufficient 
volume of blood or fluid and that this contains sufficiently strorg diuret- 
les, 1.e. diuretics can take the place of flow. . 
__® As also increased absorption in the gut or placenta, or, as in in 
flammation absorption of toxic or useless matter, and all other forms of 
blood activity. 
ei Si seat 


Sey isa iieranaee ee omer ty om, eb Ses ser ity ube 
