THE INORGANIC CONSTITUENTS OF THE URINE. 231 



etc., smaller amounts are accordingly eliminated, and it may happen, 

 indeed, that the chlorides disappear from the urine altogether. It 

 is noteworthy, moreover, that an arrest in the elimination of the 

 chlorides may then also occur even though a fair amount of salt is 

 introduced with the food. In such an event we must assume that a 

 retention is taking place in the body, in consequence of the fact that 

 the lost fluid, with its various inorganic constituents, is gradually 

 being replaced. Subsequently, when absorption of an exudate or a 

 transudate takes place, the inorganic solids find their way into the gene- 

 ral circulation, but are at once eliminated, as they are present in excess. 



The phosphates and sulphates are likewise diminished under the 

 conditions just mentioned, but do not disappear entirely, as they are 

 in part derived from the albumins during the nitrogenous metabol- 

 ism of the body. The diminution in the amount of the phosphates, 

 however, exceeds that of the sulphates, as a small fraction only of 

 the former is due to this source, while the latter are largely derived 

 from the disintegrated albumins. 



The tenacity with which the body maintains the normal composi- 

 tion of the blood is also well shown if the chlorides are gradually 

 diminished in the food, and if their elimination from the blood is 

 stimulated by the copious ingestion of diuretics. A point is soon 

 reached when the salt in question no longer appears in the urine, 

 beyond traces. If at this stage the blood is examined, it will 

 be found that the amount of chlorides is practically the same as 

 under normal conditions. There is a limit to this power of re- 

 taining the mineral salts, however, and if the chlorides are withheld 

 for a length of time and diuresis remains active, a gradual loss 

 occurs nevertheless, and in time results in the death of the animal. 

 It appears, however, that it is not the loss of chlorine which the 

 body tends to prevent, but that the sodium is the component which 

 is of prime importance. This becomes apparent when the potassium 

 salt is substituted for the sodium compound, when the same reten- 

 tion of sodium chloride occurs, while the potassium salt is eliminated 

 in the urine. In this case, also, death ultimately results from what 

 is very improperly termed " chlorine-hunger." 



If at the stage when the chlorides have practically disappeared 

 from the urine salt is added to the diet, a partial retention of this 

 occurs until the original equilibrium has been restored. After that 

 a normal elimination is again observed, and the amount then ex- 

 creted practically corresponds to the quantity ingested. 



These remarks also hold good for the phosphates and sulphates of 

 the body, though with certain restrictions. 



The bases which are found in the urine in combination with hydro- 

 chloric acid, sulphuric acid, and phosphoric acid are sodium, potas- 

 sium, calcium, magnesium, and ammonium. The latter, however, 

 occurs only in the urine of man and carnivorous animals. Calcium 

 and magnesium occur almost exclusively as phosphates, either of the 

 monacid or the diacid type. Traces, however, no doubt exist in 



