PHYSIOLOGICAL CHEMISTRY. 



globulins or nucleoalbumins. How the phosphorus is held in 

 these last-named bodies is not known, but in the nucleinic 

 acids it appears to be in oxidized form, according to some 

 authorities as metaphosphoric acid, or possibly as the pyro- 

 acid. The excreted product is orthophosphoric acid, com- 

 bined to form salts of the type MH 2 PO 4 or M 2 HPO 4 . The 

 alkali salts are soluble readily, while those of calcium and 

 magnesium are only in part soluble in water. The conditions 

 of solubility in urine are complicated by the presence of other 

 salts. 



The amount of phosphoric acid, as P 2 O 5 , excreted daily 

 varies within wide limits; according to the above analyses 

 between about 1.3 and 3.5 gm. If the urine becomes alka- 

 line through the fermentation of urea a very considerable part 

 of the phosphate may be precipitated in the form of calcium 

 and magnesium salts. One of the commonest of these is the 

 so-called triple phosphate, NH 4 MgPO 4 6H 2 O. 



THE NITROGEN EXCRETION. 



For many reasons this excretion is the most important 

 which we have to consider in connection with the urine, as it 

 gives us an insight into some of the fundamental problems 

 in metabolism. The largest part of it leaves the body as urea, 

 but the proportion excreted in other compounds cannot be 

 neglected. Considering the four substances, ammonia, urea, 

 uric acid and creatinine only, we have the following percent- 

 age distribution in the table given above : 



The urea nitrogen averages about 90 per cent of the whole. 

 The fraction is higher for the vegetarian urines than for the 



