URINE 249 



Clinical note. Renal colic is caused by the attempt to pass a stone or 

 calculus through the ureter. 



Urine is excreted more rapidly in the middle of the day, from one 

 to two o'clock, and after waking from sleep ; less rapidly between 

 two and four in the afternoon. 



Micturition is the act of expelling the urine from the bladder 

 (clinically, it is often called urination). The contraction of 

 certain muscles of the bladder wall opens the sphincter vesica and 

 the urine escapes through the urethra. 1 



Although under the control of the will after a preliminary 

 period of education, micturition is sometimes involuntary, con- 

 stituting enuresis or urinary incontinence. This may be due to the 

 presence of irritating substances in the urine which affect the mus- 

 cles of the bladder, or to too great concentration, or simply to an 

 excessive quantity of fluid, or to lack of control by the nervous 

 system or various causes of a reflex character. 



Retention of urine means accumulation in the bladder owing 

 to inability to expel it. This may be due to one or more of several 

 causes: lack of muscle tone and feeble contracting power; nervous 

 contraction (closure) of the sphincter; impaired sensibility of 

 vesical nerves; loss of spinal nerve control; obstruction at the neck 

 of the bladder, etc. This inability may be so complete that the 

 bladder becomes entirely filled and the sphincter can no longer act; 

 the urine dribbles away and the condition is one of "retention with 

 overflow" from inability of the bladder to contract. 



Suppression of urine means inability of the kidney to act; no 

 urine is excreted. 



Urine is a watery fluid of amber color, somewhat heavier than 

 water (the normal specific gravity is 1010-1020), with a charac- 

 teristic odor, and having the temperature of the body at the time 

 of voiding. Its reaction is normally acid. This is due to the 

 character of the diet of man, which in most cases contains more 

 or less of animal food. Certain salts (acid phosphates) derived 

 from this mixed diet cause the acidity of the urine. It is more 

 marked in the morning before food is taken. With a diet of 

 vegetables and cereals the reaction is neutral or, perhaps, alkaline. 



The coloring matter is derived from bile pigments; it is deep or 



1 All sphincters are opened in this manner by action of the walls of the cavity 

 which they guard. 



