THE URINE. 



Sodium and Potassium Chlorides. The sodium chloride, which repre- 

 sents nearly the whole of these two salts, is also by far the most abundant 

 mineral ingredient in the urine, forming over one-half of its inorganic 

 constituents. It is derived in great measure from the sodium chlo- 

 ride taken with the food, and is increased or diminished in quantity 

 with the variation in the amount of common salt in the diet. Various 

 circumstances, however, influence its excretion at different periods of the 

 day. Its hourly discharge is habitually least "during the night, increases 

 in the forenoon and is greatest during the latter part of the day. Ac- 

 cording to Vogel, 1 both mental and bodily exertion perceptibly increase 

 its excretion ; and even water, when taken in unusual abundance, by in- 

 creasing the activity of the kidneys, causes also a temporary augmen- 

 tation in the discharge of sodium chloride, which is subsequently followed 

 by a corresponding diminution. The average amount of the chlorides 

 discharged with the urine is about fifteen grammes per day. 



Sodium and Potassium Sulphates. The sulphates present in the 

 urine are derived partly from those which have been introduced, under 

 their own form, as ingredients of the food ; and observation has shown 

 that their quantity is increased by the medicinal administration of sul- 

 phuric acid or of sodium sulphate. The administration of sulphur or 

 the sulphurets produces a similar effect. The albuminous matters of 

 the system, furthermore, which contain sulphur as one of their con- 

 stituent elements, give rise, by their changes in the oxidizing process of 

 nutrition and excretion, to sulphuric acid and the sulphates ; since the 

 whole of their carbon, hydrogen, and nitrogen is finally discharged 

 under the form of water, carbonic acid, and urea, while the small 

 quantity of sulphur remaining appears as sulphuric acid in the sul- 

 phates. Consequently the excretion of sulphates, as shown by Vogel, 

 is increased by an abundant diet of animal food, and diminished under 

 a vegetable regimen. The sulphates are freely soluble and never appear 

 as a spontaneous precipitate in the urine. Their average quantity is 

 about 3.96 grammes per day. 



Reactions of the Urine to Chemical Tests. 



The reactions of the urine to a variety of ordinary tests form a ready 

 criterion for ascertaining its normal or abnormal constitution. The 

 more exact quantitative determination of its ingredients requires the 

 attention and skill of the professional chemist; but many of its im- 

 portant characters may be recognized by the use of simple means. 



The Application of Heat. If transparent healthy urine, of a dis- 

 tinctly acid reaction, be heated in a test-tube over a spirit lamp to the 

 boiling point, no change in its appearance is produced. If its acidity 

 be very slightly pronounced, on the other hand, it becomes turbid on 

 boiling, from a precipitation of its earthy phosphates. This is because 

 the earthy phosphates are less soluble in a hot than in a cold liquid; 



1 Analyse des Hams. Wiesbaden, 1872, p. 350. 



