PROPERTIES AND COMPOSITION OF THE URINE. 373 



tractions of its muscular walls and the action of some of the perineal mus- 

 cles, the most efficient being the accelerator urinae ; but with all this muscu- 

 lar action, a few drops of urine generally remain in the male urethra after the 

 act of urination has been accomplished. The process of evacuation of urine 

 in the female is essentially the same as in the male, with the exception of 

 the slight modifications due to differences in the direction and length of the 

 urethra. 



According to Budge, the influence of the nervous system on the bladder 

 operates through the sympathetic ; and he has described a centre in the spinal 

 cord, which presides over the contractions of the lower part of the intestinal 

 canal, the bladder and the vasa deferentia. This is called the genito-spinal 

 centre, and it has been located, in experiments upon rabbits, in the spinal 

 cord, at a point opposite the fourth lumbar vertebra. From this centre the 

 nervous filaments pass through the sympathetic nerve, communicating with 

 the ganglion which corresponds to the fifth lumbar vertebra. 



PROPERTIES AND COMPOSITION OF THE URINE. 



The color of the urine is very variable within the limits of health, and it 

 depends to a considerable extent upon the character of the food, the quantity 

 of drink and the activity of the skin. As a rule the color is yellowish or 

 amber, with more or less of a reddish tint. The fluid is perfectly transpar- 

 ent, free from viscidity, and exhales, when first passed, a peculiar, aromatic 

 odor, which is by no means disagreeable. Soon after the urine cools, it loses 

 this peculiar odor and has the odor known as urinous. This odor remains 

 until the liquid begins to undergo decomposition. The color and odor of 

 the urine usually are modified by the same physiological conditions. When 

 the fluid contains a large proportion of solid matters, the color is more intense 

 and the urinous odor is more penetrating ; and when its quantity is increased 

 by an excess of water, the specific gravity is low, the color is pale and the 

 odor is faint. The first urine passed in the morning, immediately after 

 rising, usually is more intense in color than that passed during the day, and 

 contains a relatively larger proportion of solids in solution. 



The temperature of the urine at the moment of its emission, under physio- 

 logical conditions, varies but a very small fraction of a degree from 100 

 Fahr. (37'78 C.). This estimate is the result of an extended series of obser- 

 vations, by Byasson, in 1868. 



In estimating the total quantity of urine discharged in the twenty- four 

 hours, it is important to take into consideration the specific gravity, as an 

 indication of the amount of solid matter excreted by the kidneys. Variations 

 in quantity constantly occur in health, depending upon the proportion of 

 water ; but the quantity of solid matters excreted is usually more nearly uni- 

 form. It must also be taken into account that differences in climate, habits 

 of life, etc., in different countries, have an important influence upon the daily 

 quantity of urine. Parkes collected the results of twenty-six series of observa- 

 tions made in America, England, France and Germany, and found the aver- 

 age daily quantity of urine in healthy male adults, between twenty and forty 



