THE URINE. 



79 



To take the Specific Gravity. This is usually done by means 

 of the urine-meter (Fig. 15). The instrument ought to be tested 

 by placing it in a cylindrical vessel filled with 

 distilled water to ascertain that its zero is cor- 

 rect. 



.1010 



_!030 



.1040 



(a.) Fill a tall cylindrical vessel with urine, 

 and place the urinometer in it. Bring the 

 vessel to the level of the eye, and as soon 

 as the instrument comes to rest, read off" the 

 mark on its stem opposite the lower surface 

 of the meniscus against a bright background. 



Precautions. 1. The vessel must be so wide 

 that the urinometer can float freely and not touch 

 the sides. 2. The instrument must be dry before 

 being placed in the fluid. 3. The urine itself 

 must be clear, and free from air-bubbles on the 

 surface; the latter can be readily removed by 

 means of a fold of blotting-paper. N.B. It is 

 always necessary to take the specific gravity of 

 the "mixed" urine of twenty-four hours. 



Low Specific Gravity. All causes which increase 

 the water of the urine only e.g., drinking on 

 an empty stomach ; after hysteria ; in Diabetes 

 insipidus or Polydipsia. N.B. If continually 

 below 1015, suspect Diabetes insipidus or chronic 

 Bright' s disease. 



High Specific Gravity. When the urine is 

 concentrated; Diabetes mellitus, due to a large 

 amount of grape sugar; first stages of acute 

 fevers ; rapid wasting of the tissues, especially if 

 associated with sweating or diarrhoea. It is 

 highest normally three to four hours after a meal ; 

 and as it varies during the day, it is necessary to 

 mix the urine of the twenty-four hours, and test 

 the specific gravity of a sample of the " mixed 

 urine." N.B. If above 1025 and the urine be pale, suspect 

 saccharine diabetes. 



5. Determination of the amount of Solids from the Specific 

 Gravity. By Christisoris formula (" Haser-Trapp's coefficient") 

 " multiply the last two figures of a specific gravity expressed in 

 four figures by 2-33. This gives the quantity of solid matter in 



Fig. 15. 

 Urinometer. 



