348 EXCRETION 



quantity rapidly returns to the normal standard during convalescence. 

 Most of the chlorides of the urine are in simple watery solution ; but 

 a certain proportion of sodium chloride exists in combination with 

 urea. 



The daily elimination of sodium chloride is about one hundred and 

 fifty-four grains (10 grams). The great variations in its proportion in 

 the urine, under different conditions of alimentation, etc., will explain 

 the differences in the estimates given by various authorities. 



Stdphates. In normal urine the sulphates are in the form of salts 

 of potassium and of sodium. It is probable that these in great part 

 pass into the urine with the products of proteid katabolism and are 

 unimportant. A certain proportion of the sulphates, however about 

 ten per cent is in a peculiar form of combination with putrefactive 

 products from the large intestine, notably indol, phenol, cresol and 

 skatol. These organic matters are in part absorbed by the blood and in 

 part discharged in the feces. That portion absorbed by the blood is 

 carried to the liver and there combines with sulphates, forming the so- 

 called conjugate, or ethereal sulphates. These sulphates are not toxic, 

 like the organic matters with which they are united, and they are elimi- 

 nated from the blood by the kidneys. One of the chief products of 

 this kind is potassium indoxyl-sulphate. This may be made to yield 

 indigo by treatment with certain reagents and is called indican. The 

 urinary indican is supposed to represent putrefactive processes in the 

 large intestine. 



Although urinary indican is often found in disease, when present in 

 what may be called normal urine it exists in very small quantity. It 

 has been estimated, however, that -^ to \ of a grain (0.005 to 0.02 gram) 

 is discharged in twenty-four hours (Jaffe). It is unfortunate that this 

 product is called indican, as it is likely to be confounded with vegetable 

 indican (C 26 H 31 NO 17 ), which is a glucoside. The formula for indoxyl- 

 sulphuric acid is C 8 H 7 NSO 4 . Urinary indican is C 8 H 7 NSO 4 K. 



Phosphates. The urine contains phosphates in a variety of forms ; 

 but inasmuch as it is not known that any one of the different combina- 

 tions possesses peculiar relations to the processes of katabolism, as 

 distinguished from the other phosphates, the phosphatic salts may be 

 considered together. 



The phosphates exist constantly in the urine and are derived in part 

 from food and in part from the tissues. Like other inorganic matters, 

 they are associated with the nitrogenous constituents of the organism, 

 and when these are changed into excrementitious substances and are 

 separated from the blood by the kidneys, they pass with them and are 

 discharged from the body. 



