H12 PHYSIOLOGY 



THE AVERAGE COMPOSITION OF THE URINE. Several analyses 

 of the day's urine under varying conditions of food have already been given 

 (v. pp. 757, 780). The following may be taken as a fair average for an adult 

 man on ordinary mixed diet : 



Total amount of urine = 1500 c,c. 



This contains about 60 grm. of solids, of which 25 grm. are inorganic and 

 35 grm. organic. These are distributed as follows : 



INORGANIC CONSTITUENTS ORGANIC CONSTITUENTS 



Sodium chloride . . . . 15-0 grm. Urea . . 30-0 grm. 



Sulphuric acid . . .2-5 Uric acid . .0-7 



Phosphoric acid . . .2-5 



Creatinine . . . .1*0 

 Hippuric acid , . . 0-7 

 Other substances . .2-6 



Potassium .... 3*3 

 Ammonia . . . .0*7 

 Magnesia . . .0-5 



Lime . . . .0*3 

 Other substances . . . 0-2- 



The quantity of urine will naturally vary with the water leaving the 

 body by the kidneys, and therefore according to the habit of the individual 

 with regard to the intake of fluids and with his occupation. Thus after 

 copious sweating the total amount may fall to 400 c.c. in the course of the 

 day. If large draughts of liquid be taken it may rise to 3000 c.c. or more. 

 There are also diurnal variations in the amount secreted, depending probably 

 largely on the circulation through the kidneys. The secretion is at a mini- 

 mum during sleep, and especially between 2 and 4 o'clock in the morning. 

 It is at its maximum during the first hours after rising, and increases generally 

 after each meal. Muscular exercise may also give an initial increase owing 

 to the greater vigour of the circulation associated with exercise. If the 

 exercise is severe enough to cause sweating or is carried to fatigue, there 

 may be a consequent diminution in the amount of urine secreted. 



THE INORGANIC CONSTITUENTS OF THE URINE 



(a) ACID RADICALS. The chlorides of the urine are derived almost 

 entirely from the chlorides of the food. Though essential constituents of 

 the body fluids, it does not seem that the chlorides enter into organic com- 

 bination with the constituents of the cells. The output of chlorides, which 

 normally varies from 6 to 10 grm. Cl. in the course of the day, will therefore 

 depend on the amount of chlorides taken in with the food. If these be 

 withdrawn altogether, the chlorides may almost disappear from the urine, 

 although the circulating blood contains practically the same amount of 

 chlorides as in the normal individual, showing that the body retains the 

 chlorides necessary for the proper carrying out of the vital processes as 

 long as possible. Chlorides may also disappear from the urine temporarily 

 under various pathological conditions. This is especially marked in cases 

 of acute pneumonia. 



