PROPERTIES AND COMPOSITION OF URINE 563 



is dissolved in ammonia and a little zinc chloride solution is added 

 the mixture turns red with a green fluorescence; urochrome, on the 

 contrary, does not yield fluorescent solutions. 



Both of these pigments are closely related to the bile-pigments and, 

 therefore, to hemoglobin. They yield the pyrrole reactions and 

 strongly resemble substances which are obtainable from Bilirubin by 

 reduction. Urobilin, or its parent-substance urobilinogen is a con- 

 stant constituent of the feces, but before the identity of the two pig- 

 ments was realized the urobilin in the feces received a separate name, 

 Stercobilin. The quantity of these pigments in the urine is distinctly 

 increased in all fevers, also in hemorrhage and in conditions involving 

 the destruction of red blood-corpuscles, and in diseases of the liver. 



Uroerythrin is the pigment which frequently gives a red color to 

 urinary sediments, particularly to sediments of uric acid, which, owing 

 to its presence, may appear like grains of cayenne pepper. It does not 

 yield fluorescent solutions and is rapidly decolorized by light. The 

 normal color of solutions is pink, but strong sulphuric acid changes 

 this to carmine, and alkalies to green. Uroerythrin is believed not to 

 be related to bilirubin but to be derived from Skatole. The quantity is 

 increased by muscular activity, profuse perspiration, alcohol, immod- 

 erate eating, fevers and diseases of the liver. 



The presence of urobilinogen in the feces and the probable deriva- 

 tion of uroerythrin from skatole render an alimentary origin of these 

 pigments very probable. It is likely that urochome and urobilin arise 

 by bacterial decomposition of the bile-pigments in the lower intestine. 

 In confirmation of this view it is found that strong Intestinal Putre- 

 faction leads to an increase of the urobilin output while exclusion of 

 bile from the intestine reduces the output to zero. If the exclusion of 

 bile from the intestine be due to mechanical occlusion of the bile-ducts, 

 then bile-pigments, but not urobilin, appear in the circulation and in 

 the urine. 



THE PROPERTIES AND COMPOSITION OF URINE. 



The volume of the urine which is voided daily necessarily varies 

 very greatly with the quantity of water which is drunk, the quantity 

 of water contained in the food, the amount of fluid lost from the body 

 by perspiration and a variety of other factors such as the presence or 

 absence of Diuretics such as Caffein or Theobromin in the diet, or hyper- 

 activity of the posterior lobe of the pituitary body which may lead to 

 a chronic hyper secret ion of a dilute urine containing no sugar; a con- 

 dition known as Diabetes Insipidus. 



The Specific Gravity of the urine necessarily varies with its volume, 

 usually fluctuating between 1.008 and 1.030. The reaction is usually 

 acid, but immediately after a meal an alkaline reaction, the "alkaline 

 tide" may frequently be observed, and on a purely vegetable diet 

 the urine is not infrequently alkaline. The sulphur and phosphorus 



