REACTION OF THE URINE. 431 



mucous membrane, in which are mucous glands, glands of Littre, 

 and opening into it in the male are two compound racemose 

 glands, Cowper's glands. In the female urethra the epithelium is 

 stratified. In the male urethra it is stratified near the meatus, 

 transitional in the prostatic portion, and elsewhere columnar. 



THE URINE. 



Quantity. The amount of urine voided by an adult' in 

 twenty-four hours is about 1500 c.c., although it may vary within 

 normal limits from 1200 c.c. to 1700 c.c. In health the increased 

 drinking of fluids and lessened formation of the perspiration will 

 increase the amount of urine excreted, while the excretion will be 

 diminished if the quantity of liquids drank is lessened or if the 

 perspiratory glands are more active. It is a matter of common 

 observation that in summer the urinary flow is less than it is in 

 winter. 



Color. The color is ordinarily yellow, though it may be, 

 even in health, almost colorless or reddish brown. The urinary 

 pigments are urochrome, urobilin, uroerythrin, and hematopor- 

 phyrin. 



Urochrome. This is the essential pigment to which the yellow 

 color is due. It has been demonstrated that when alcoholic solu- 

 tions of pure urochrome are treated with aldehyd a reducing 

 action is produced on the pigment and urobilin is produced. This 

 would indicate that urochrome is an oxidation-product of urobilin. 



Urobilin. This is the same as stercobilin of the feces, and is 

 probably formed from the bilirubin of the bile. Urobilin exists 

 in small amount in the urine, and principally in the form of a 

 chromogen, to which the name urobilinogen has been given. Uro- 

 bilin and hydrobilirubin are regarded by some as identical. Hop- 

 kins states that the origin of urinary bilirubin is probably three- 

 fold from absorption of the ready-formed pigment in the bowel ; 

 from direct production in the liver ; and from reduction of the 

 blood-pigment in the organ, independently of hepatic agency. 



Uroerythrin. This coloring-matter is that which gives the 

 characteristic color to the pinkish deposits of urates. It exists 

 in small amount, but it is always present in normal urine. 



Hematoporphyrin. Although normally present in but small 

 amount, this substance may exist pathologically in considerable 

 quantity. 



Reaction. The reaction of the mixed urine passed in twenty- 

 four hours is acid to litmus, due to the presence of sodium dihy- 

 drogen phosphate, NaH 2 PO 4 , or, as it is more commonly called, 

 acid sodium phosphate. 



The acidity of the urine is subject to considerable variation. 

 It is increased after exercise and after the consumption of animal 



