376 THE URINE. 



Physical Properties of the Urine. 



The urine is a clear, amber-colored fluid, of a watery consistency, and 

 with a distinctly acid reaction. As a general rule, its transparency is so 

 nearly perfect that no appearance of turbidity is perceptible by ordinary 

 diffused daylight. It contains, however, a very small quantity of 

 mucus from the urinary bladder, which may be rendered visible as a 

 faint opalescence when a sunbeam is made to pass through it in a lateral 

 direction. If the urine be allowed to remain at rest for a few hours in 

 a cylindrical glass vessel, the mucus gradually subsides, forming a very 

 light cloudy mass at the bottom and leaving the supernatant fluid en- 

 tirely clear. The ingredients of the urine itself are all therefore in a 

 state of complete solution. While still warm and fresh, the urine has a 

 peculiar but not offensive odor, which disappears on cooling and may 

 be then restored by gentle heating. The average specific gravity of 

 healthy urine, in the adult, is from 1020 to 1025 ; and its daily quantity 

 is about 1200 cubic centimetres. 



Variations of the Urine in Quantity, Acidity, and Specific Gravity. 

 The urine does not present uniformly the same characters, but varies 

 normally from hour to hour, in each individual, at different periods of 

 the day. It is usually discharged from the bladder five or six times in 

 the twenty-four hours, and each specimen shows more or less variation 

 in its physical properties. This variation depends upon the changing 

 conditions of the body, as to rest, exercise, food, drink, sleeping, and 

 waking. In the same person, leading a uniform mode of life from day 

 to day, the diurnal variations of the urine follow each other with great 

 regularity ; although in different persons, whose habits are different, they 

 may not be altogether the same. Asa general rule, the urine which 

 collects in the bladder during the night and is first discharged in the 

 morning is strongly colored, of high specific gravity, and has a very 

 distinct acid reaction. That passed during the forenoon, on the other 

 hand, is pale and of comparatively low specific gravity ; often falling 

 so low as 1018 or even 1015. At the same time, its acidity diminishes 

 or even disappears altogether ; so that at this time in the day the urine 

 is frequently neutral or slightly alkaline. Toward noon, its density and 

 depth of color increase, and its acidity returns. All these properties 

 become more strongly marked during the afternoon and evening ; and 

 toward night the urine is again deeply colored and strongly acid, and 

 has a specific gravity of 1028 or 1030. 



The following instances will serve to show the general characters of 

 this variation : 



OBSERVATION FIRST. March 20th. 



Urine of 1st discharge, acid, sp. gr. 1025. 



" 2d ' alkaline, " 1015. 



3d " neutral, " 1018. 



" 4th " acid, " 1018. 



" 5th " acid, " 1027 



