560 THE EXCRETION OF URINE 



of the alveolar air at night in a typical case was 7.4 per cent and after 

 rising 6.63. Leathes also showed that forced breathing causes a marked 

 increase in the alkalinity of the urine, a result which confirms those of 

 Haldane, Meakin, etc., referred to elsewhere in this volume (page 381). 



THE SOLID CONSTITUENTS 



In a person living on an ordinary diet the most important organic 

 and inorganic constituents of the urine are as follows : 



TOTAL SOLIDS (40 TO 60 GRAMS) IN ONE LITER OF NORMAL URINE 

 ORGANIC CONSTITUENTS, 25-40 GM. INORGANIC CONSTITUENTS, 15-25 GM. 



Urea, 20-35 gm. Sodium chloride (NaCl), 8-15 gm. 



Creatinine, 1.0-1.5 gm. Phosphoric acid (P 2 O 5 ), 2.5-3.5 gm. 



Uric acid, 0.5-1.25 gm. Sulphuric acid, (SO,), 2-2.5 gm. 



Hippuric acid, 0.1-1.7 gm. Potassium (K,O), 2-3 gm. 



Other constituents (ethereal sulphates, Sodium (Na,O), 4-6 gm. 



oxalic acid, urinary pigments, etc.), Calcium (Cab), 0.1-0.3 gm. 



1.5-2.3 gm.' Magnesium (MgO), 0.2-0.5. 



Ammonia (NH 8 ), 0.3-1.2 gm. 

 Iron (in pigment), 0.001-0.010. 



(Compiled from MosenthaPs 4 figures.) 



These urinary salts are present in the blood, and are only excreted by 

 the kidney. An investigation of the mechanism of renal excretion must 

 therefore include a study of the relationship existing between the con- 

 centration of the urinary salts in the blood and in the urine. We shall 

 briefly review the chief biochemical relationships of the most important of 

 these constituents and then give tables showing the quantitative changes 

 which they undergo in various diseases. 



The Organic Salts of Normal Urine 



Nitrogenous Constituents. The greater number of the organic salts of 

 the urine are made up of bodies which contain nitrogen, and which are 

 derived from the protein element of nutrition. The proteins, which form 

 the chief building material of the body, are broken up into their con- 

 stituent amino acids in the intestinal tract and absorbed as such by the 

 blood. Portions of these acids are taken up by the tissues to repair and 

 to replace those proteins which have been discarded, and the remaining 

 protein, in excess of the body need for amino acids, is deamidized, the 

 major portion of the carbon, oxygen and hydrogen being oxidized to 

 form C0 2 and water, and the lesser portion of these elements being com- 

 bined with the nitrogen to form urea, ammonia, uric acid, etc. A similar 

 fate later awaits the nitrogen moiety which found a place in the tissues, 

 and which is replaced in turn by new nitrogenous bodies.* 



*For further details see page 645. 



