45 



The amount of solids in the urine may be estimated from 

 the specific gravity b5' Christison's formula ("Haser-Trapp's 

 coefficient"). " Multiply the last two figures of a specific 

 gravity expressed in four figures by 2.33. This gives the 

 quantit/ of solid matter in every 1,000 parts." The num- 

 ber of grams in 1000 cc. 



Example. — Suppose a patient passes 1400 cc of urine in 

 twenty-four hours and the specific gravity is 1020, then, 20 

 times 2.33 equals 46.60 grams in 1000 cc. To ascertain 

 the amount in 1400 cc. 1000 is to 1400 as 46.60 is to x. 

 1400 times 46.60 equals 65240.00, this divided by 1000 equals 

 6.'5.24 grams, of solids in 1400 cc. of urine. 



The formula is purely empirical, and is not applicable 

 where the variations are very marked, as in saccharine dia- 

 betes and some cases of Bright's disease. 



The normal or total solids or ".solid urine" is about 70 

 grams (2 oz.) in twenty-four hours. 



The reaction of human urine is usually slightly acid. The 

 acidity being chiefly due to acid sodium phosphate, and acid 

 urates and very slightly to free acids — lactic, acetic, oxalic 

 etc. During digestion two or three hours after a meal, the 

 urine becomes neutral or alkaline. With a vegetable diet 

 the excess of alkali causes an alkaline urine. In herbivora 

 it is alkaline ; in carnivora it is very acid. 



When urine is freely exposed to the air it undergoes two 

 fermentations, acid and alkaline. The urine at first becomes 

 slightly more acid, from the formation of lactic and acetic 

 acids. (This is denied by some). Then it gradually be- 

 comes neutral, and finally alkaline from putrefaction. It 

 becomes lighter in color, turbid, and a whitish heavy pre- 

 cipitate occurs. A pellicle forms on the surface, it swarms 

 with bacteria and it has an ammoniacal odor, which is due 

 to the splitting up of the urea. The urea is split up by a 

 ferment said to be formed by the Micrococcus ureae. 



224. Place some urine aside for some days in a warm 



