INFLUENCE OF NERVES AND OTHER CONDITIONS. 427 



5. Those bodies which are complete^ decomposed, as glycerin, resins, give rise to no special 

 derivatives in the urine. 



6. Many substances combine and appear as conjugated compounds in the urine, e.g., the 

 origin of the hippuric acid by conjugation ( 260), the conjugation of sulphonic acid ( 262), 

 and the formation of urea by synthesis from carbamic acid and ammonia (Drechsel) ( 256). 

 After the use of camphor, chloral, ov butylchloral, a conjugated compound with glycuronic acid 

 (an acid nearly related to sugar) appears in the urine. Taurin and sarcosin unite with 

 sulphaminic acid. When bromophenol is given, it unites with mercapturic acid, a body nearly 

 related to cystin ( 268). 



7. Tannic acid, C ]4 H 10 O 9 , takes up H 2 0, and is decomposed into two molecules of gallic acid 



= 2(C 7 H 6 5 ). 



8. The iodates of potash and soda are reduced to iodides ; malic acid (C 4 H 6 5 ) partly to 

 succinic acid (C 4 H 6 4 ) ; indigo-blue (C 16 H 10 N,Oo) takes up hydrogen and becomes indigo-white 



(C lfi H 12 N 2 2 ). 



9. Some substances do not pass into the urine at all, e.g., oils, insoluble metallic salts and 

 metals. 



276. INFLUENCE OF NERVES AND OTHER CONDITIONS. At present 

 we are acquainted merely with the influence of the vaso-motor nerves on the 

 filtration of the urine through the renal vessels. Each kidney seems to be supplied 

 with vaso-motor nerves, which spring from both halves of the spinal cord (Nicolaides). 

 As a general rule, dilatation of the branches of the renal artery, chiefly the vasa 

 afferentia, must raise the pressure within the glomeruli, and thus increase the 

 amount of water filtered through them. The more the dilatation is confined to the 

 area of the renal artery alone, the greater is the amount of the urine. [As yet we 

 know the nervous system influences the secretion of urine only in so far as it modi- 

 fies the pressure and velocity of the blood-current in the kidney. We have no 

 satisfactory evidence of the existence of direct secretory nerves in the kidney.] 



1. Renal Plexus and its Centre. Section of the nerves of the renal plexus 

 the nerves around the renal artery generally causes a considerable increase in the 

 secretion of urine, hydruria or polyuria ; sometimes, on account of the great rise 

 of the pressure within the glomeruli, albumin passes into the urine, and there may 

 be rupture of the vessels of the glomeruli, leading to the passage of blood into the 

 urine. The nerve-centre for the renal nerves lies in the floor of the fourth 

 ventricle, in front of the origin of the vagus. Injury to this part of the floor of the 

 fourth ventricle, e.g., by puncture (piqure), may increase the amount of urine 

 (diabetes insipidus), which is sometimes accompanied by the simultaneous appear- 

 ance of albumin and blood in the urine (CI. Bernard). Section of the parts which 

 lie directly in the course of these fibres, as they pass from their centre to the kidney, 

 produces the same effects. Close to this centre in the medulla, lies the centre for 

 the vaso-motor nerves of the liver, whose injury causes diabetes mellitus ( 175). 

 Eckhard found that stimulation of the vermiform process of the cerebellum produced 

 hydruria. In man, stimulation of these parts by tumours or inflammation, &c, 

 produces similar results. 



2. Paralysis of Limited Vascular Areas. If, simultaneously with the paralysis 

 of the nerves of the renal artery, the nerves of a neighbouring large vascular area 

 be paralysed, necessarily the blood-pressure in the renal artery area will not be so 

 high, as more blood flows into the other paralysed province. Under these circum- 

 stances, there may be only a temporary, or, indeed, no increase of urine, provided 

 the paralysed area be sufficiently large. There is, a moderate increase of urine for 

 several hours after section of the splanchnic nerve. This nerve contains the renal 

 vaso-motor nerves (which, in part, at least, leave the spinal cord at the first dorsal 

 nerve and pass into the sympathetic nerve), but it also contains the vaso-motor 

 nerves for the large area of the intestinal and abdominal viscera. Stimulation of 

 this nerve has the opposite effect (CI. Bernard, Eckhard). [The polyuria thus 

 produced is not so great as after section of the renal nerves, because the splanchnic 

 supplies such a large vascular area, that much blood accumulates in that area, and 

 also because all the renal nerves do not run in the splanchnics.] 



