Diseases of the Urinary Organs. 193 



On the other hand suppression of the urinary secretion 

 may occur in connection with profuse perspirations in hot weather, 

 with prolonged diarrhoea, or with privation of water, and in such 

 cases the liquid becomes concentrated and irritating and there 

 is a disposition to precipitate its solids under slight disturbing 

 causes. As conducive to such precipitation may be named 

 foreign solid bodies, bacterial ferments and probably the goitre 

 poison since gravel and calculus are common in goitrous regions. 



There are two forms of elimination through the kidneys. 

 \, filtration; 2, secretion. 



1 . Filtration is referred to the glomeruli, and is determined by 

 the relative blood pressure. Increase of pressure causes increase 

 of watery , transudation. Digitalis increases heart action and 

 arterial pressure, and accidentally urination. Excessive consump- 

 tion of water and watery liquids increases intravascular ten- 

 sion, and the amount of urine. 



2. Secretion is referred to the columnar epithelium of the 

 convoluted tubes. It is by the elective afiEinity or selective 

 power of this epithelium that the solids of the urine are ab- 

 stracted from the blood and passed into the urine. Crystals of 

 uric acid have been found in these cells and it is supposed 

 that the abundance of water furnished by the glomeruli, irri- 

 gating these convoluted tubes, dissolves and washes on the 

 various solids and other products with which the epithelial cells 

 are charged. The protoplasm of the cells becomes saturated 

 with the urea, uric acid, hippuric acid coloring matter (indican, 

 urochrome, etc.), and this is washed out, passing by exosmosis 

 to the liquid of lesser density with which the tubes are filled. 



Nervous Control of Urinary Secretion. 



An electric current through the renal plexus of the sym- 

 pathetic (vasormotor) lessens, or suppresses urinary secretion 

 (inhibition). 



Cutting the nerves of this plexus causes excessive vaso-di- 

 lation, renal pulsations synchronous with heart beats and arterial 

 pulse, and great increase of urine. A similar increase comes 

 from the application of cold to the surface, from fatigue, from 

 heat exhaustion, from irritation of the floor of the fourth ventricle 



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