174 URINALYSIS. 



the probable presence of sugar. The determination of specific 

 gravity is made with a urinometer. 



7. Solids. Xormal urine, when freshly voided, is free from visi- 

 ble solids, save a few epithelial scales. The visible solids of abnor- 

 mal urine may be estimated by means of the centrifuge. The quan- 

 tity of invisible solids in normal or pathological urine may be esti- 

 mated by multiplying the last two figures of the number represent- 

 ing the specific gravity by 2.33. This gives the number of grams 

 in a liter of the sample. Thus, in urine whose specific gravity is 

 1.030, the number of grams of solids held in solution would be 

 30X2.33, or 69.9 grams. The amount of solids eliminated by the 

 urine, 1,500 c.c. in twenty-four hours, would be represented by the 

 equation : 20 X 2. 33 X 1 . 5 = 69. 9 grams. The quantity of solids for 

 twenty-four hours is affected by age, diet, exercise, etc., the average 

 quantity for a person of 145 pounds being 61 grams. A reduction 

 of solids indicates renal diseases (with a tendency toward uraemia) 

 and defective elimination. The importance of knowing the amount 

 of urine passed in twenty-four hours is evident. 



Laboratory exercise No. 66. Make a physical examination of some 

 sample of urine, performing* all the tests indicated above. 



2. CHEMICAL URINALYSIS. 



1. Urea, CO (NH 2 ) 2 . The normal quantity of urea in the urine 

 is about one-half of all the solid constituents, or about 35 grams. 

 It is formed in the liver as the result of destructive metabolism of 

 the tissues and the splitting up of nitrogenous food principles. An 

 excess of urea occurs in acute diseases, such as fevers, in some liver 

 affections, such as diabetes, and accompanies excessive physical and 

 mental exertion, and indicates tissue waste A deficiency occurs in 

 chronic diseases. The average elimination of urea for an adult for 

 twenty-four hours is estimated at 33 grams. The percentage in the 

 urine is estimated by means of the Doremus ureometer as indicated 

 in the following method : Fill the long arm of the ureometer with 

 hypobromite. By means of the graduated pipette add 1 c.c. of 

 urine by compressing the nipple gently and steadily. The hypo- 

 bromite causes the liberation of nitrogen gas, which collects in the 



