THE URINE 



463 



chloride and a little hydrochloric acid to the urine. A white precipitate 

 of barium sulphate results. The acid prevents the .precipitation of 

 phosphates. 



Organic or Ethereal Sulphates are compounds of sulphuric acid 

 with such bodies as indol, skatol, phenol, cresol. Their presence may 

 be shown by precipitating the inorganic sulphates and phosphates 

 with alkaline barium chloride, filtering, and heating the filtrate 

 almost to boiling with-strong HC1. By this means the organic sulphates 

 are decomposed, and form a faint white cloud of barium sulphate. 

 If they are in excess, a white precipate forms. 



" Neutral Sulphur " is the sulphur present in urine, not in the form 

 of sulphate, but as an integral part of the molecule of the organic 

 substance e.g., cystin. 



About 2i grammes of sulphuric acid (S0 3 ) are excreted daily. 

 The inorganic sulphates are derived mainly from the protein katabolism 

 of the food. Inorganic sulphates e.g., Epsom salts are not ingested 

 as such, owing to their unpleasant bitter taste. 



The ethereal sulphates are conjugates of sulphuric acid with toxic 

 bodies formed by putrefaction of protein in the intestine, especially 

 of the tyrosin and tryptophan portions of the molecule. The phenol, 

 cresol, indol, and skatol, there formed are absor-bed into the portal 

 circulation, and combined in the liver with sulphuric acid, and so 

 rendered harmless. 



Normally, the inorganic sulphates are about ten to twenty times 

 more abundant than the organic. The relative proportion, however, is 

 not, as has been supposed, a direct measure of the putrefactive pro- 

 cesses in the intestine. It has been found that this proportion, and 

 that of the neutral sulphur, varies with the amount of nitrogen in the 

 diet, as shown in the following table : 



Nitrogen-Rich Diet. . Nitrogen-Poor Diet. 



Volume of urine 

 Total nitrogen 

 Total SO : , . . 



Inorganic . . 



Organic 



Neutral 



1,170 c.c. 



16-8 grammes. 



3-64 



3-27 (90 %) 



0-19 (5-2%) 

 0-18 (4-8 %) 



385 c.c. 



3-00 grammes. 



0-76 



0-46 (60-5 %) 



0-10 (13-2%) 



0-20 (26-3 %) 



The best guide to the extent of the intestinal putrefactive processes 

 is now believed to be given by the amount of indican present in the 

 urine. Indican is the indoxyl-sulphate of potassium formed from 

 the indoxyl brought to the liver in the portal blood (see p. 450). 





NH.C 8 H 5 OH 



Indoxyl 



H 2 0. 



Acid 



potassium 

 sulphate 



Ind : can 



