644 THE SECRETION OF URINE. 
The course taken by the nerves is very variable. The nerves are derived 
from the sympathetic chain. From the ganglia lying on the head of the 
thirteenth rib, or from the cord immediately below this, is given oft' a 
large nerve (larger than the continuation of the sympathetic chain), 
which perforates the crus of the diaphragm, and is called the large 
splanchnic nerve. Between this ganglion and the next two or three 
ganglia below, are given off three or four smaller filaments, known as the 
small splanchnic nerves. (It must be noted that this terminology is not 
comparable with that employed in human anatomy, where the term 
splanchnics is confined to the nerves given oft" by the sympathetic chain 
while in the thoracic cavity.) These large and small splanchnics form a 
plexus situated behind the suprarenals, and from which filaments are 
given oft' to the cceliac and superior mesenteric ganglia and solar plexus. 
From the plexus behind the suprarenals arise a number of filaments, 
which form a meshwork in the fat and connective tissues between the 
suprarenal and kidney, and then pass to the kidney around, and closely 
applied to, the renal artery. 
According to v. Wittich, 1 the renal nerves in the rabbit, dog, and man 
consist of two parts ; one part of them forms a plexus closely investing 
the renal artery, while the other consists of several filaments which enter 
the kidney parallel to the vessels, and can be traced along these as far 
as the cortex. 
The termination of these nerves in the kidney has been recently inves- 
tigated by Berkeley,' 2 using Golgi's method. He finds that from the vascular 
nerves fine filaments arise to be distributed throughout the cortical and 
medullary regions in the form of a vast open network. The glomeruli are 
surrounded by a wide-meshed plexus of fibres, having terminal end knobs, 
approximated closely to Bowman's capsule, but not penetrating that membrane, 
nor passing to the glomerular capillaries. Fibres also pass off from the vascular 
plexus to be distributed upon the convoluted tubes, with terminations which 
penetrate the membrana propria of the tube, presumably to enter the cement 
substance between the epithelial cells. Berkeley looks upon these latter nerves 
as probably secretory in function. 
With regard to the connection of the renal nerves with the central 
nervous system, Bradford 3 has shown that, so far as the efferent nerves 
to the renal vessels are concerned, these leave the spinal cord through 
the anterior roots. Most of the fibres are contained in the eleventh, 
twelfth, and thirteenth dorsal nerve roots. 
Influence of blood flow on secretion of urine. — We are now in a 
position to consider the influence exerted by changes in the circulation 
•through the kidney on the secretion of urine. It must be remembered 
that a rise of general blood pressure does not necessarily carry with it an 
increased pressure in the glomerular capillaries or an increased blood flow 
through the kidney. Thus, under many conditions, a rise of general 
blood pressure is brought about by a constriction of all the visceral 
arteries, including those of the kidney, and such constriction is more 
than sufficient to counteract the effects of the increased blood pressure. 
If we take a tracing of the kidney volume, for instance, in asphyxia, we 
1 Konigsberger, Med. Jahrb., Wien, 1860, Bd. iii. S. 52 (quoted from Heidenhain in 
Hermann's " Handbuch "). 
2 Journ. Path, and Bacterid., Edin. and London, 1893, vol. i. p. 406. 
3 Journ. Physiol., Cambridge and London, 1889, vol. x. p. 358. 
