646 THE SECRETION OF URIXE. 
division of all the renal nerves, stimulation of the cord causes a large 
expansion of the kidney and brings back the urinary flow. 
Influence of the splanchnics. 1 — The effects of stimulating the splanch- 
nic nerves are very similar to those obtained from the stimulation of the 
cord. As in the latter case, a large rise of general blood pressure is 
produced, but the constriction of the renal vessels more than counteracts 
the effects of this rise, so that the kidney shrinks and the flow of urine 
is diminished or abolished. The effects of dividing the splanchnics vary 
in different animals. In the rabbit, where, in consequence of the extent 
of the vascular area supplied by this nerve, a considerable fall of general 
blood pressure is produced, no increase in the urinary secretion is 
observed. In the dog, on the other hand, the lasting effect on the aortic 
pressure is insignificant, so that the relaxation of the kidney vessels 
caused by the section induces a largely increased flow through this organ, 
and a marked increase in the flow of urine. 
Influence of renal nerves. — Division of the renal nerves on one side 
causes vasomotor paralysis in the organ of that side. The kidney there- 
fore swells, and the flow of urine is increased. The swelling and 
secretion is still further increased if the general blood pressure be raised 
by stimulation of the splanchnics or spinal cord. Stimulation of the 
renal nerves causes constriction of the vessels and diminished flow of 
urine. 
Bradford 2 has brought forward evidence to show that v-aso-dilator 
fibres run to the kidney with the constrictors, in the eleventh, twelfth, and 
thirteenth dorsal nerve roots. If the anterior roots of these nerves be 
stimulated with induction shocks, repeated at the rate of one per second, 
the effect is often a marked swelling of the kidney without any rise of 
blood pressure sufficient to account for the enlargement, A similar 
active dilatation of the vessels may be brought about reflexly by stimulat- 
ing the posterior roots of these nerves. We have no direct experimental 
evidence as to the influence of this active vascular dilatation on the 
renal secretion, although it is extremely probable that a similar condi- 
tion is the chief factor in the production of the extreme hydruria met 
with in hysteria and other nervous affections. a 
Constriction of renal artery. — In some of the earliest researches on the 
connection between the blood flow through the kidney and the urinary 
secretion, it was sought to affect the circulation by direct mechanical 
constriction of the renal artery. Hermann, 3 who carried out experi- 
ments of this nature under Ludwig's guidance, showed that when the 
artery was constricted to a considerable extent, the result was a dimin- 
ished flow of urine. If the constriction were carried so far that the 
circulation of the kidney was entirely stopped, the flow of urine instantly 
ceased. So far these results are those one would expect on. the filtration 
hypothesis. It is found, however, that the flow of urine is not restored 
at once on relieving the constriction, and that after a few minutes' total 
cessation of the renal circulation, more than an hour may elapse between 
the restoration of the circulation and the recommencement of the secre- 
tion. We have seen that in the case of lymph formation, where a 
process of filtration almost certainly comes into play, a temporary 
ischamiia increases the permeability of the vessel wall, so that, on the 
1 See especially Eckhard, Beitr. :. A ant. u. Physiol. {Eckhard), Giesseu, 1S69, Bd. iv. 
S. 132, and 153-193. 
2 Loc. tit. "• Loc. tit. 
