430 URAEMIA AND AMMONIiEMIA. 



exposed in an auimal, by making an incision in the lumbar region, on stimulating 

 the medulla oblongata directly with electricity, we may observe the kidney itself 

 becoming paler, the palor appearing in a great many small spots on the surface of 

 the organ, corresponding to the distribution of the interlobular arteries.] 



[Cohnheim showed that the composition of the blood has a remarkable effect 

 on the renal circulation. Some substances (water and urea), when injected into 

 the blood, cause the kidney first to shrink and then to expand, while sodic acetate 

 dilates the kidney, even after all the renal nerves are divided an operation which 

 is very difficult indeed. Provided all the renal nerves be divided, these effects 

 would indicate the existence of some local intra-renal vaso-motor mechanism govern- 

 ing the renal blood-vessels. The general blood-pressure is not thereby modified ; 

 nor need we wonder at this, as ligature of one renal artery does not increase the 

 pressure in the aorta.] 



[The reciprocal relation between the skin and the kidneys is known to every 

 one. On a cold day, when the skin is pallid, owing to contraction of the cutaneous 

 vessels, the amount of urine secreted is great, and conversely, in summer less urine 

 is passed than in winter. Washing the skin of a dog for two minutes with ice-cold 

 water causes a great contraction of the kidney.] 



The perfusion of blood through a living excised kidney is materially in- 

 fluenced by the substances mixed with the blood perfused. This effect may in part 

 be due to the action of these chemical ingredients upon the nuclei of the endo- 

 thelial lining of the blood-vessels, especially the capillaries, or the effects upon the 

 muscular fibres of the blood-vessels. 



[Strychnin seems to cause contraction of the renal vessels, independently of its action on the 

 general vaso-motor centre. Brunton and Power found that digitalis caused an increase of the 

 blood-pressure (dog), but the secretion of urine was either at the same time diminished, or it 

 ceased altogether. The latter result was due to contraction of the renal blood-vessels, but 

 when the aortic blood-pressure began to fall, the amount of urine secreted rose much above 

 normal, i.e., when the arteries had begun to relax.] 



During fever, the renal vessels are probably contracted in consequence of the stimulation of 

 the renal centre by the abnormally warm blood (Mcndelson). 



The repeated respiration of CO is said to produce polyuria, perhaps in consequence of 

 paralysis of the renal vaso-motor centre. 



Action of the Vagus. According to CI. Bernard, stimulation of the vagus at the cardia in- 

 creases the urinary secretion, while at the same time the blood of the renal vein becomes red. 

 This nerve may contain vaso-dilator nerve-fibres corresponding to the fibres in the facial 

 nerve for the salivary glands ( 145). 



277. TTBJEMIA -AMMONIiEMIA. Symptoms of Uramiia. After excision of the kidneys, 

 nephrotomy, or ligature of the ureter ; in man, also, as a result of certain diseased conditions 

 of the kidney, leading to the suppression of the secretion of urine, there is developed a series of 

 characteristic symptoms which are followed by death. The condition is called uraemic intoxi- 

 cation or uraemia. There are marked cerebral phenomena, drowsiness, and deep coma, and 

 occasionally local or more general spasms. Sometimes there is delirium ; Cheyne-Stokes pheno- 

 menon is often observed ( 111, II.), and there may be vomiting and diarrhoea, while in the 

 fluids voided, as well as in the expired air, ammonia may sometimes be detected. 



The cause of these phenomena has been ascribed to the retention in the blood of those sub- 

 stances which normally are excreted by the urine, but as yet it has not been definitely ascer- 

 tained which of these substances causes the phenomena : 



1. The first thought is to ascribe them to the retention of the urea. V. Voit found that 

 dogs exhibited uraemic symptoms if they were fed for a long time on food containing urea and 

 little water. Meissner found that in nephrotomised animals, the uraemic symptoms were 

 hastened by the injection of urea into the blood. The injection of a moderate amount of urea 

 in perfectly healthy animals is not followed by uraemic symptoms, probably because the urea 

 is rapidly excreted by the kidneys ; 1 to 2 grins. [15 to 30 grains] so injected produce comatose 

 symptoms in rabbits^ 



2. The injection of ammonium carbonate produces symptoms resembling those of uraemia, 

 so that v. Frerichs thought that the urea was decomposed in the blood, yielding ammonium 

 carbonate ammonisemia. Demjankow observed uraemic phenomena after nephrotomy, if at 

 the time he injected urea-ferment into the blood ( 263). Feltz and Ritter obtained uraemic 

 symptoms in dogs by injecting salts of ammonia. 



