INORGANIC CONSTITUENTS OF THE URINE. 423 



thirty to forty-five grains, the normal quantity being from one hundred and fifty to one 

 hundred and sixty grains. This quantity is less than the amount contained in the 

 ingesta, and under these circumstances there is a gradual diminution in the nutritive 

 activity. "This tact demonstrates the necessity of adding chloride of sodium to the 

 food." It is an interesting pathological fact that, in all acute febrile disorders, the pro- 

 portion of chlorine in the urine rapidly diminishes and is frequently reduced to one hun- 

 dredth of the normal amount. The quantity rapidly increases to the normal standard 

 during convalescence. Most of the chlorides of the urine are in simple watery solution ; 

 but a certain proportion of the chloride of sodium exists in combination with urea. 



The daily elimination of chloride of sodium is about one hundred and fifty-four grains 

 (Robin). 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. 



Sulphates. There is very little to be said regarding the sulphates, beyond the general 

 statements we have made concerning the inorganic principles of the urine. The propor- 

 tion of these salts in the urine is very much greater than in the blood, in which there 

 exists only about 0'28 of a part per thousand. Inasmuch as the proportion in the urine is 

 from three to seven parts per thousand, it seems probable that the kidneys eliminate 

 these principles as fast as they find their way into the circulating fluid, either from the 

 food or from the tissues. Like other principles derived in great part from the food, the 

 normal variations in the proportion of sulphates in the urine are very great. It is unne- 

 cessary to consider in detail the variations in the amount of sulphates discharged in the 

 urine, depending upon the ingestion of different salts or upon diet, for all the recorded 

 observations have been followed by the same results, and they show that the ingestion of 

 sulphates in quantity is followed by a corresponding increase in the proportion eliminated. 



Thudichum estimates the daily excretion of sulphuric acid at from 23 to 38 grains. 

 Assuming, with Robin, that the sulphates consist of about equal parts of sulphate of 

 potassa and sulphate of soda, with traces of sulphate of lime, the quantity of salts would be 

 from 22*5 to 3V'5 grains of sulphate of potassa and an equal quantity of sulphate of soda. 



Phosphates. The urine contains phosphates in a variety of forms; but, inasmuch as 

 it is not known that any one of the different combinations possesses peculiar relations to 

 the process of disassimilation, as distinguished from the other phosphates, the phosphatic 

 salts may be considered together. 



The remarks which we have just made with regard to the chlorides and the sulphates 

 are applicable, to a certain extent, to the phosphates. These salts exist constantly in the 

 urine, and they are derived in part from the food and in part from the tissues. Like other 

 inorganic matters, they are united with the nitrogenized elements of the organism, and, 

 when these are changed into excrementitious principles and are separated from the blood 

 by the kidneys, they pass with them and are discharged from the organism. 



It becomes a question of importance, now, to consider how far the phosphates are 

 derived from the tissues, and what proportion comes directly from the food. This point 

 is peculiarly interesting, from the fact that phosphorus has been shown to exist in the 

 nerve-tissue, and it has been inferred that the excretion of phosphates represents, to some 

 extent, the physiological wear of the nervous system. 



All observers agree that the quantity of phosphates in the urine is in direct relation 

 to the proportion in the food, and that an excess of phosphates taken into the stomach is 

 immediately thrown off by the kidneys. It is a familiar fact, indeed, that the phosphates 

 are deficient and the carbonates predominate in the urine of the herbivora, while the 

 reverse obtains in the carnivora, and that variations, in this respect, in the urine, may be 

 produced by feeding animals with different kinds of food. Verdeil made some very 

 interesting comparative analyses of the blood for the alkaline phosphates in the herbivora, 



