COMPOSITION OF THE URINE. 439 



Aromatic Substances. Hippuric acid or benzamido-acetic acid 

 belongs to the aromatic series, by reason of its containing the 

 benzene nucleus. Besides this, there are other aromatic substances 

 which come from the food and also from the proteids of the tissues. 

 Among these are phenol, kresol, pyrocatechin, sometimes inosit, and 

 various carboxyacids. Indoxyl, which is produced by the oxida- 

 tion of the indol that is absorbed from the intestine, and skatoxyl, 

 produced in the same manner from skatol, also occur in urine. 



Dextrose. Ordinary urine contains dextrose to the amount 

 of from 0.08 to 0.18 gram per diem. The presence of dextrose 

 in normal urine has been and still is denied, but the most recent 

 investigations seem to leave no doubt upon this much mooted 

 question. 



We have seen that alimentary glycosuria may occur when 

 an excessive amount of sugar is ingested. In diabetes mettitut* 

 the quantity of dextrose in the urine may be very great, 500 

 or 600 grams being excreted in a single day. The methods of 

 recognizing the presence of dextrose have been previously referred 

 to (p. 87). 



Lactose. The presence of this variety of sugar in the urine 

 constitutes lactosuria, and this condition of the nursing mother's 

 urine is quite constant. Lactose is formed by the mammary gland, 

 absorbed by the blood, and eliminated by the kidneys. It must 

 be inverted before it can be changed into glycogen ; this inversion 

 takes place when lactose is ingested with the food, but when 

 absorbed by the blood from the mammary gland, it does not occur. 

 Under these circumstances lactose enters the blood directly as 

 lactose and is excreted in the urine. 



Lactosuria is a condition which has escaped general recognition, 

 and in speaking of it Hopkins says : " If the urine exhibits the 

 following characters, the presence of lactose is established almost 

 without the possibility of doubt : It should reduce copper and 

 bismuth solution ; but with the fermentation-test, it should give 

 negative results for the first twenty-four hours of the experiment, 

 and it should give no definite crystalline precipitate with the 

 phenylhydrazin test when this is directly applied. On the other 

 hand, after boiling with 5 per cent, sulphuric acid for a short time 

 the urine should, if first neutralized with ammonia, give the 

 phenylhydrazin test readily : crystals of dextrosazon should be thus 

 obtained, and with proper precautions galactosazon crystals may 

 also be distinguished. Although the lactose is converted by the 

 mineral acid into dextrose and galactose, fermentation is not 

 always to be obtained after treatment, as the large amount of 

 sulphate which is present after neutralizing the acid interferes 

 with the growth of the yeast. If the reducing power of the 

 urine is estimated, this should be found increased after boiling 

 with mineral acid, but unaffected by boiling with citric acid." 



