166 NUTRITIONAL PHYSIOLOGY 



originating in the liver and elsewhere. Second in abun- 

 ^lance among the urinary constituents we ordinarily find 

 the mineral salts. The quantity of these depends in a 

 large measure upon the amount in the diet, and as sodium 

 chlorid is the one taken most freely, so it will generally be 

 the principal inorganic compound in the urine. The 

 chlorids of the mixture are accompanied by phosphates and 

 sulphates. These are not to any extent salts which have 

 been eaten, but, like the urea, they represent modified 

 fragments of protein molecules. The phosphates come 

 from a limited class of proteins, largely from those of the 

 cell-nuclei; the sulphates arise from all proteins. 



The minor ingredients of the urine are very numerous. 

 Those of most interest are the bodies which carry the ni- 

 trogenous waste over and above that handled as urea. 

 To one unfamiliar with organic chemistry a list of their 

 names can have little meaning. The substance_creatinin, 

 already mentioned, is provisionally regarded as indicative 

 of the rate of true endogenous metabolism, the inevitable 

 gradual wasting of the nitrogenous tissues. Another com- 

 pound which has attracted much attention on account of its 

 apparent relation to several pathologic conditions is uric 

 acid. A certain amount of this is produced during fasting 

 and is not increased by the taking of many kinds of food. 

 The addition to the diet of meats leads to a larger formation 

 of uric acid. A maximum quantity is elaborated when 

 glandular tissues, such as liver, kidneys, and sweetbreads, 

 are eaten. These articles contain an exceptional propor- 

 tion of jiuclear material rich in the proteins just referred 

 to as sources of phosphates. The same proteins are evi- 

 dently uric-acid formers. The chief peculiarity of uric 

 acid is its slight solubility, which renders its complete 

 excretion difficult and uncertain. Retention of this crys- 

 talline substance has been held accountable for the pain- 

 ful symptoms of gout and of a good deal that goes by the 

 inclusive name of rheumatism. 



We have by no means exhausted the list of normal urin- 

 ary constituents, but the student must be referred to other 



