Solid Matter in Urine. 353 



is on the first day of experiment No. 71 with S. A. B., when less than half this 

 amount, i. e., 25.51 grams, was eliminated. Considering the averages of the 

 experiments, the lowest amount recorded is in experiment No. 71, 34.99 grams, 

 and the highest amount is in experiment No. 59, 52.93. In general the 

 average amount of total solids during the different experiments is not far from 

 40 grams per day. 



On the individual days of the same experiment, there is usually- an increase 

 on the second day after which the amount remains fairly constant. 



An inspection of the data of the different experiments with the same subject, 

 S. A. B., shows an average daily elimination of total solids as follows : Experi- 

 ment No. 71, 34.99 grams; experiment No. 73, 37.13 grams; experiment No. 

 75, 44.22 grams; and experiment No. 77, 51.35 grams. Leaving out the first 

 day of each of these experiments, since as a rule it is lower than the other days, 

 the averages become 38.15, 36.79, 45.15, and 54.42 grams respectively. Conse- 

 quently, it appears that in experiments Nos. 71 and 73, the subject S. A. B. 

 eliminated practically the same amount of total solids each day. In experiment 

 No. 75, there was an average elimination of nearly 10 grams more, while in 

 experiment No. 77 the average amount per day was about 10 grams greater than 

 that during experiment No. 75. 



While the average amount per day of total solids in the series of 2-day 

 experiments is not far from 40 to 45 grams, yet individual fluctuations may be 

 very considerable as, for example, in the 2-day experiment No. 82, in which on 

 the first day there were 37.13 grams, and on the second, 54.93 grams. 



Ratio of the Total Solids to the Specific Gravity. 



Knowing the volume of urine excreted per day and having an accurate record 

 of the specific gravity, it is possible by factors to compute in many instances 

 the amount of total solids. This method of computation has frequently been 

 used for the approximations of the clinician. 



The various organic and inorganic substances dissolved in normal urine have 

 widely varying physical properties and hence solutions of varying density. 

 A solution of 100 grams of sodium chloride in a liter of water has a density 

 at 15 of 1.073, while a solution of urea 1 to 10 has a density of but 1.028. 



With ordinary conditions of diet, however, it has been found that the total 

 solids in 1 liter of urine may be reasonably approximated by multiplying 

 the last two figures of the specific gravity (as ordinarily expressed in three 

 decimal places) by 2.33. Thus 650 cc. of urine of a specific gravity of 1.027 

 would contain total solids as follows : 27 X 2.33 X -650 = 40.89. It is stated 

 by some writers, that if the specific gravity is less than 1.018, more accurate 

 results can be obtained by using the factor 2.0. 



In normal urines, therefore, this factor is by no means constant. Since 

 determinations were made of volume, specific gravity and total solids in the 



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