836 APPENDIX. 



flask, which is then heated till the vapor of ammonia escapes by a nar- 

 row tube. The sugar solution is then allowed to flow from a burette 

 into the flask until the blueness has disappeared, the solution being 

 kept boiling all the time. The blueness is apt to disappear suddenly, 

 and care should therefore be taken toward the end of the process. 

 Calculate as in Fehling's method. 



3. Estimation of sugar by fermentation. In the case of saccharine 

 urine, it is allowable as a single test to use the following method: Take 

 specific gravity of urine before and after fermentation. Each degree 

 of specific gravity lost by the urine represents one grain of sugar per 

 ounce of urine. 



4. Sugar may also be estimated by adding yeast to urine, and col- 

 lecting the carbon dioxide evolved. The carbon dioxide is a measure 

 of the amount of sugar present. 



5. The estimation may also be done by the saccharimeter, an instru- 

 ment for the estimation of the degree of polarization which a ray of 

 light undergoes in passing through a solution of sugar, either to the left 

 or to the right. 



Urea, CO (NHg)?. The properties and relations of urea have been 

 treated of at some length in the chapter upon excretion. There re- 

 mains to be described the method of its quantitative estimation in the 

 urine. There are two chief methods, viz. : 



(i.) Hypobromite Method. One of the forms of apparatus employed 

 in this method (Russell and West's) consists of (a) a water-bath sup- 

 ported by three iron bands, arranged as a tripod. The bath is provided 

 with a cylindrical depression, and with a hole, into which fits a perfo- 

 rated india-rubber cork; (&) a bulb tube with a constricted neck; (c) a 

 glass rod provided with an india-rubber band at one extremity; (d) a 

 pipette of five cubic centimetres capacity; (e) a graduated glass collect- 

 ing tube; (/) a spirit lamp; (y) a wash-bottle with distilled water; (h) 

 hypobromous solution. The hypobromous solution is made in the fol- 

 lowing way: three and a half ounces (100 grm.) of solid caustic soda is 

 dissolved in nine ounces (250 grm.) of distilled water. When the solu- 

 tion is cold, seven drachms (25 c.c.) of pure bromine are to be added 

 carefully and gradually. The mixture is not to be filtered; it keeps 

 badly, and for this reason it should be made shortly before it is required ; 

 or the solution of caustic soda in water may be made in large quantities 

 as it does not undergo any change, the bromine in the proper propor- 

 tion being added at the time it is required for use. 



Method. Fill the pipette to the mark on the stem with the urine to 

 be examined; pour the 5 c.c. of urine thus measured out into the bulb; 

 fill up the bulb tube as far as the constricted neck with distilled water 

 from the wash-bottle; insert the glass rod (c) in such a way that the 

 india-rubber band at the extremity fills up the constricted neck; the 



