CHAPTER YII. 



PEOPERTIES AND COMPOSITION OF THE HEINE. 



General physical properties of the urine Quantity, specific gravity, and reaction 

 Composition of the urine Urea Origin of urea Compounds of uric 

 acid Hippurates and lactates Creatine and creatinine Oxalate of lime 

 Xanthine Fatty matters Inorganic constituents of the urine Chlorides 

 Sulphates Phosphates Coloring matter and mucus Gases of the 

 urine Variations in the composition of the urine Variations with age and 

 sex Variations at different seasons and at different periods of the day 

 Variations produced by food Urina potus, urina cibi, and urina sanguinis 

 Influence of muscular exercise Influence of mental exertion. 



THE importance of an exact knowledge of the properties 

 and composition of the urine has long been recognized by 

 physiologists ; and our literature is full of observations, more 

 or less valuable, upon this subject, dating from the discovery 

 of urea by Hillaire Rouelle, 1 in the latter part of the last 

 century, to the present time. It is impossible, however, to 

 follow out in detail even the most important of the chemical 

 researches upon the different urinary constituents, without 

 exceeding the limits of pure human physiology ; and the ob- 

 servations of the earlier authors, Scheele, Bergmann, Cruick- 

 shank, 3 Fourcroy, Yauquelin, Frout, and many others, have 



1 MILNE-EDWARDS, Lemons sur la physiologie, Paris, 1862, tome vii., p. 395. 

 This author gives a very full account of the earlier chemical researches into the 

 composition of the urine, which resulted in a description of the properties of 

 urea. The observations of Rouelle were quite imperfect ; but the more elabo- 

 rate researches of Scheele, Bergmann, and others, which will be cited further on, 

 gave a pretty correct idea of the chemical characters of this important excretion. 



8 Cruickshank was the first to describe the formation of crystals of the 

 nitrate of urea. He added to the concentrated urine an equal bulk of nitrous (?) 



