CHAP. XXXIV.] COMPOSITION OF HEALTHY URINE. 



499 



which are not required for the wants of the system, and salts which, having 

 performed certain offices by their passage through the tissues, are no longer 

 required, and certain other saline compounds, which, like many of the 

 organic constituents, are formed by oxidation in the processes concerned 

 in nutrition. The inorganic salts are composed of chlorides, sulphates, and 

 phosphates, with traces of silica, and the bases entering into the compo- 

 sition of these salts are, potash, soda, lime, and magnesia. It is exceedingly 

 difficult to ascertain the precise composition of the salts as they were ori- 

 ginally held in solution in the urine ; for, in the processes of evaporation, 

 and subsequent incineration, certain decompositions take place, which en- 

 tirely alter their nature. The quantities in which these substances occur, 

 vary in different specimens of urine, and the published analyses of the se- 

 cretion in a healthy state, will be found to differ considerably from each 

 other. This difference arises chiefly from the variation in the proportion of 

 water ; for, by calculating the relation existing between the quantities of the 

 several solid constituents, it will be found to be nearly the same in all. 



The following is an analysis of healthy human urine, by Dr. Miller. The 

 per-centage composition of the solid matter is shown in a separate column. 

 Specific gravity, 1 020 : 



Water 956'80 



Solid matter. . . . . . .' '. 42-98 



In 100 of 

 Solid matter. 



Organic matters 

 29-822 



Fixed Salts 

 13-158 



Urea . 

 Uric acid . . . 

 Alcohol extractive . 

 Water extractive . 

 Vesical mucus. 

 Muriate of ammonia 

 Chloride of Sodium. 

 Phosphoric acid 

 Sulphuric acid . 

 Lime 

 Magnesia . 

 Potash . 

 \ Soda 



99996 



Urea (C. 2 R^ Z 2 ) constitutes nearly half of the solid matter of healthy 

 urine, and the secretion itself contains from 2-5 to 3-2 per cent, of this sub- 

 stance The quantity, however, is much increased by exercise, or by a purely 

 animal diet. According to Lehmann, when a highly nitrogenous diet is taken, 

 a quantity of urea equal to nearly five-sixths of -the nitrogenous matter intro- 

 duced is eliminated by the kidneys. A considerable quantity of urea, how- 

 ever, is formed when no food whatever is taken, or when a non-nitrogenous 

 diet is adhered to for a considerable period, which clearly shows that a large 

 proportion of urea is derived from the disintegration of the tissues, by the 

 process of secondary assimilation. *It is often detected in abnormal quantity 

 in the urine of patients suffering from rheumatism, and certain febrile com- 

 plaints ; and, in various diseases, it may sometimes be obtained from this 

 fluid in very large quantities. This condition is very commonly associated 



