BY DR. LAUDER BRUNTON. 543 



2.33, the product represents very closely the weight of the 

 total solids contained in 1000 parts, by weight, of urine. 

 Subsequent observers have determined that whilst Ohristison's 

 formula yields very correct results when applied to urines of 

 specific gravities above 1018, for urines of lower specific gravity 

 greater accuracy is obtained by substituting the factor 2 for 

 2.33. 



The following example will suffice to show the method of 

 calculating approximately the total solid matter excreted in 

 the urine in twenty-four hours : 



A man passes in twenty-four hours 1575 cubic centimetres 

 of urine of specific gravity 1023, and it is desired to obtain an 

 approximate estimate of the total urinary solids. 



1st. We find the total solids (expressed in any particular 

 units of weight) contained in 1000 parts (expressed in the 

 same units of weight) by Dr. Christison's formula, thus, if the 

 unit be the gramme, and the quantity of solid matter in 1000 

 grammes be represented by x, 



x = (1023 1000) 2.33 = 53.59. 



2d. We require to know the weight of the whole of urine. 

 As its density is 1023, and the quantity 1576 cubic centimetres, 

 the weight in grammes is at once found by the following 

 proportion : 



1000 : 1023 :: 1575 :x 

 x 1575 



1000 



3d. Knowing the weight in grammes of the urine of twenty- 

 four hours, and the approximate weight of total solid matters 

 in 1000 parts, by weight, of urine, we obtain the total solids 

 passed in twenty-four hours expressed in grammes : 



1000 : 53.59 :: 1611 : x 

 x = 86.33 grammes. 



It is to be noted that the result obtained by such calcula- 

 tions is merely an approximation to the actual number which 

 would be ascertained by the direct method, to be immediately 

 described ; the approximation is, however, sufficiently close to 

 be useful. 



192. Determination of the Total Solid Matters con- 

 tained in Urine. If we know the total volume of urine 

 passed in twenty-four hours, and it be desired to ascertain, by 

 direct weighing, the total quantity of solid matter contained 

 in it, 10 or 15 cubic centimetres of the mixed urine are poured 

 from a very accurately graduated pipette into a weighed porce- 

 lain or glass capsule, which is heated over the water-bath, 



