URINE 451 



Inositol occasionally occurs in the urine in albuminuria, diabetes 

 mellitus, and diabetes insipidus. It is claimed also that copious water- 

 drinking causes this substance to appear in the urine. Inositol was at 

 one time considered to be a sugar but is now known to be hexahy- 

 droxybenzene, as the above formula indicates. It is an example of a 

 non-carbohydrate in whose molecule the H and O are present in the 

 proportion to form water. In other words it has the formula of the 

 hexoses, i.e., CeH^Oe. Inositol occurs widely distributed in the 

 vegetable kingdom, and because of this fact the theory has been voiced 

 that it represents one of the first stages in the conversion of a car- 

 bohydrate into the benzene ring. It is found in the liver, spleen, 

 lungs, brain, kidneys, suprarenal capsules, muscles, leucocytes, testes, 

 and urine under normal conditions. 



EXPERIMENT 



i. Detection of Inositol (Scherer). Acidify the urine with concentrated nitric 

 acid and evaporate nearly to dryness. Add a few drops of ammonium hydroxide 

 and a little calcium chloride solution to the moist residue and evaporate the mixture 

 to dryness. In the presence of inositol (o.ooi gram) a bright red color is obtained. 



For a more satisfactory test, which is also more time-consuming, see Salkowski's 1 

 modification of Scherer's test. 



LAIOSE 



This substance is occasionally found in the urine in severe cases of 

 diabetes mellitus. By some investigators laiose is classed with the 

 sugars. It resembles fructose in that it has the property of reducing 

 certain metallic oxides and is levorotatory, but differs from fructose 

 in being amorphous, non-fermentable, and in not possessing a sweet 

 taste. 



MELANINS 



These pigments never occur normally in the urine, but are present 

 under certain pathological conditions, their presence being especially 

 associated with melanotic tumors. Ordinarily the freshly passed urine 

 is clear, but upon exposure to the air the color deepens and may at 

 last be very dark brown or black in color. The pigment is probably 

 present in the form of a chromogen or melanogen and upon coming 

 into contact with the air oxidation occurs, causing the transforma- 

 tion of the melanogen into melanin and consequently the darkening 

 of the urine. 



It is claimed that melanuria is proof of the formation of a visceral 



1 Salkowski: Zeit. physiol. chem., 69, 478, 1910. 



