LACTOSURIA. CHOLURIA. 189 



birth. Its presence indicates the absorption of the sugar 

 from the fluid in the mammary gland. It may appear 

 with the interruption of nursing or from stagnation of 

 the milk in the gland. When the gland is well developed 

 and lactose is found in the urine during the period of 

 nursing it shows merely that the secretion of milk is 

 abundant. The chemical reactions of lactose are very 

 similar to those of glucose. The principal differences are 

 that lactose ferments with yeast with difficulty or not at 

 all, and that its power of reduction is less than that of 

 glucose. Still, the distinction between the two as they 

 occur in urine is a matter of some difficulty. 



395. Try the fermentation test with compressed 

 yeast, as in Experiment 32, upon urine containing glucose 

 and that containing lactose, and notice that the former 

 ferments, with the evolution of carbon dioxid, and the 

 latter does not. 



396. Try Barfoed's test (Experiment 28) upon the 

 two kinds of urine, and notice that it responds to glucose, 

 but not to lactose. In this test it must be borne in mind 

 that the other reducing substances of normal urine urates, 

 creatinin., etc. may cause a reduction of the copper salt. 



CHOLURIA. 



In examining the urine for bile two classes of com- 

 pounds are sought for: the biliary acids and the biliary 

 pigments. The biliary acids do not normally occur in 

 urine, except in small amounts. The pigments are more 

 commonly found. In the freshly-passed urine usually 

 only bilirubin is present, but by oxidation it may be 

 changed to biliverdin, etc. Urine which contains bile is 

 generally of a yellowish- to greenish- brown color, and the 



