THE MICROSCOPE IN DIAGNOSIS. 301 



ranee of the microscopic appearance of these common 

 things has led to ludicrous mistakes. 



The amount of urine passed in each twenty-four hours 

 varies from 20 to 50 ounces, holding in solution from 600 

 to 700 grains of solid matter. The amount, both of solids 

 and fluids, varies according to the amount of fluids im- 

 bibed, the action of the skin, etc. The quantity of urine 

 should be considered in relation with its specific gravity, 

 since diminished urine with greater specific gravity may 

 occur in diarrhoea, etc., and imbibed fluids may cause 

 greater quantities with lessened specific gravity. 



The average specific gravity of healthy urine is 1.020. 

 It may be measured by means of the specific gravity bot- 

 tle, or with the urinometer, a loaded glass bulb with 

 graduated stem. According to Dr. G. Bird, each degree 

 of the urinometer represents 2.33 grains of solids in 1000. 

 Thus specific gravity 1.020 represents 46.60 grains solid 

 matter, and 953.40 water in 1000 of urine. 



Another table of Dr. Bird's shows that the specific 

 gravity figures indicate nearly the amount of solids in 

 each fluid ounce. Thus 1010 shows 10 grains of solids, 

 1020 about 20 grains, etc. Yet this is only approximate. 



High specific gravities (above 1025) are found in dia- 

 betes (from sugar), in concentrated urine from fevers or 

 other causes, in acute renal dropsy, and sometimes from 

 large quantities of albumen in solution. Low specific 

 gravities (below 1015) occur when the quantity is exces- 

 sive, especially in diabetes insipidus,in lardaceous disease 

 of the kidney, and chronic cases of Bright's disease. 



UREA. 



Urea is the vehicle by which nearly all the nitrogen of 

 the exhausted tissues is removed from the system, and 

 its retention is often attended with fatal ursemic poison- 

 ing of the blood. The quantity naturally eliminated de- 



