356 



PHYSIOLOGICAL CHEMISTRY. 



vegetables and fruits contain relatively large quantities of 

 potassium salts of organic acids, and such substances may 

 have been consumed here. It is important to note further the 

 amounts of ammonia in these urines. This form of excretion 

 has been frequently overlooked in calculating urine analyses, 

 but as will appear below the nitrogen in it makes up an appre- 

 ciable fraction of the total excretion. In this place it will be 

 well also to call attention to the ratio of urea to uric acid, 

 which was formerly frequently stated too high because of 

 faulty methods used in determining the latter, as referred to 

 above. From the above tables it appears in this way : 



We may turn now to a consideration of individual constit- 

 uents in the excretion. 



THE EXCRETION OF ALKALI SALTS. 



The alkali salts found in the urine come from the sodium 

 chloride consumed as such in salted food, and in part from 

 potassium salts in the juices of meat and in vegetables. In the 

 analysis of the ash of muscle given some pages back chlorine 

 as well as potassium is shown. Chlorine is found, although 

 usually in small amount, in the ash of all vegetable substances. 

 In the latter, however, especially in the cereals, potassium 

 phosphate is the characteristic constituent of the ash. On a 

 cereal diet we should expect the urine, in consequence, to show 

 a relatively high potash and phosphoric acid content. The 

 ash of potatoes contains in the mean over 60 per cent of potas- 

 sium oxide while the chlorine is in excess of the sodium. 

 With a mixed diet therefore the composition of the alkali salts 

 in the urine must be variable and difficult of explanation. As 

 the alkali compounds are practically all soluble they are ex- 

 creted almost solely by the urine and to a small extent only by 



