CHAPTEE VII 



ORIGIN OF KATABOLIC CONSTITUENTS OF URINE 



CONTENTS. 1. General characteristics and composition of human urine. 

 2. Formation of urea. 3. Formation of uric acid and the purine bodies. 4. Forma- 

 tion of creatine and creatinine. 5. Formation of hippuric acid and aromatic 

 substances (ethereal sulphates). 6. Formation of pigments and chromogens 

 (urochrome, urobilin, uroerythrin, indican). 7. Formafion of non- nitrogenous 

 organic acids (oxalic acids, lactic acids, volatile fatty acids). 8. Carbohydrates of 

 normal and pathological urine (glucose, lactose, animal gum, acetone, glycuronic 

 acid). 9. Proteins of normal and pathological urine (serum -albumin, serum- 

 globulin, fibrinogen, enzymes). 10. Inorganic constituents of urine (chlorides, 

 sulphates, alkaline and earthy phosphates, carbonates, ammonium compounds). 

 11. Toxicity of urine and uraemia. 1 Bibliography. 



WE stated in the introduction to the last chapter that the kidneys 

 represent the principal organ of excretion in the animal body. 

 All the waste products, in fact, which originate in the foods that 

 are introduced into, and absorbed from the digestive canal leave 

 the body sooner or later by the kidneys, with the exception of the 

 few substances permanently retained, of those which are con- 

 stituents of the body at the moment of death, and of those, lastly, 

 which are eliminated in the form of gas or fluid by the other 

 excretory systems the lungs, surface of the skin, and internal 

 mucous surfaces, particularly the mucous membrane of the 

 intestines. If we sum up the products not eliminated by the 

 kidneys, they obviously form a very minor quantity in comparison 

 with the sum of the metabolites that are thus excreted. The 

 predominating importance of the renal apparatus is plain, when 

 we consider the chemical nature of the excreta eliminated by the 

 kidneys. The majority of the nitrogenous compounds, i.e. the 

 waste products of the proteins, which form the main substrate of 

 living protoplasm, are discharged with the urine. 



I. So much can be gathered from the composition and 

 character of the Urine as to the general metabolism of the body 

 and its principal organs and tissues, that it is no wonder this 



1 EDITORIAL NOTE. Owing to the impossibility of giving adequate directions 

 for laboratory work in connection with this chapter, the technical instructions 

 contained in certain passages of the Italian text have been entirely omitted from 

 the English version. 



377 



