Organic Matter in Urine. 



359 



amount, especially on the first days of a fast, it is important to see what 

 variations exist in the actual amounts of organic matter excreted per day. 

 Since the organic matter is made up in large part of nitrogen containing 

 material, it may be taken as a rough measure of the amount of protein metab- 

 olism, and therefore measurements of this total amount are of especial interest. 

 The total organic matter of the urine is estimated by deducting the weight 

 of ash from the weight of total solids, and hence the values thus obtained are 

 affected by the errors incidental to the determinations of both ash and total 

 solids. In determining total solids, it is probably true that the analyses give 

 results which are somewhat too low, since even in drying in a vacuum, there is 

 unquestionably loss of material. It is likewise true that in the determination 

 of crude ash there must be more or less volatilization of inorganic material 

 which tends to make the results for crude ash too low. Hence it is seen that 

 the two most striking errors in the determinations of these two factors may 

 be said to more or less compensate when the values thus obtained are used 

 for the indirect determination of the total organic matter. It is reasonable 

 to suppose then, that the determinations of organic matter are approximately 

 correct. Furthermore, as has been pointed out previously, since the same 

 method was employed for all experiments the results are strictly comparable. 



1 Not determined for individual days, calculated as shown on p. 29. 



2 Includes amount calculated in urine spilled. See p. 243. 



The amounts of organic matter found by deducting the total ash from the 

 total solids are recorded for each day of each experiment (table 195). It 

 is here to be noted that the apportionments of the total organic matter on 



