INORGANIC CONSTITUENTS OF THE TJKINE. 211 



of the inorganic matters of the urine is derived from the 

 food. 



From the fact that the inorganic matters discharged in 

 the urine are generally the same as those introduced with 

 the food, and that they vary in proportion with the consti- 

 tution of the food, it is difficult to ascertain how far their 

 presence and quantity in the urine represent the processes 

 of disassimilation. One thing, however, is certain : that the 

 organic constituents of the food, the blood, the tissues, and 

 the urine, are never without inorganic matter in considera- 

 ble variety ; and it is more than probable that the presence 

 of these salts in a tolerably definite proportion influences the 

 processes of absorption and secretion and has an important 

 bearing upon nutrition ; but we are as yet so imperfectly 

 acquainted with the processes of nutrition of the tissues, that 

 we cannot follow out all the relations of the inorganic mat- 

 ters, first to nutrition, and afterward to disassimilation. 



Chlorides. Almost all of the chlorine in the urine is in 

 the form of chloride of sodium ; the amount of chloride of 

 potassium being insignificant and not of any special physio- 

 logical importance. It is unnecessary, in this connection, to 

 describe the well-known properties of common salt ; and the 

 means for determining its presence and proportion in the 

 urine are fully treated of in works upon physiological chem- 

 istry. All that we have to consider is its importance and sig- 

 nificance as a urinary constituent. 



By reference to the table of the composition of the urine, 

 it is seen that the proportion of chloride of sodium is subject 

 to very great variations, the range being from three to eight 

 parts per thousand. This at once suggests the idea that the 

 quantity excreted is dependent to a considerable extent upon 

 the amount taken in with the food ; and, indeed, it has been 

 shown by numerous observations that this is the fact. 1 The 



1 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, p. 162. 

 XEUBAUER AND YOGEL, A Guide to the Qualitative and Quantitative Analysis of 



