420 PHYSIOLOGICAL CHEMISTRY 



urine is increased as a result of X-ray treatment. The purine bases 

 form a higher percentage of the total purine excretion in the case of 

 the monkey, sheep and goat than in man. 



EXPERIMENT 



i. Formation of the Silver Salts. Add an excess of magnesia mixture 1 to 

 25 c.c. of urine. Filter off the precipitate and add ammoniacal silver solution 2 

 to the filtrate. A precipitate composed of the silver salts of the various purine 

 bases is produced. The purine bases may be determined quantitatively by means 

 of Kruger and Schmidt's method (see page 533), or Welker's method (see page 

 535). 



2. Inorganic Physiological Constituents 

 Ammonia 



Next to urea, ammonia is the most important of the nitrogenous 

 end-products of protein metabolism. Ordinarily about 2.5-4.5 per 

 cent of the total nitrogen of the urine is eliminated as ammonia and 

 on the average this would be about 0.7 gram per day. Under normal 

 conditions the ammonia is present in the urine in the form of the 

 chloride, phosphate, or sulphate. This is due to the fact that combina- 

 tions of this sort are not oxidized in the organism to form urea, but are 

 excreted as such. This explains the increase in the output as ammonia 

 which follows the administration of the ammonium salts of the mineral 

 acids or of the acids themselves. On the other hand, when ammonium 

 acetate and many other ammonium salts of certain organic acids are 

 administered no increase in the output of ammonia occurs since the salt 

 is oxidized and its nitrogen ultimately appears in the urine as urea. 

 Acid-forming foods (see page 613) also increase the ammonia output, 

 whereas the administration of alkalies or of base-forming foods decreases 

 the excretion of ammonia. 



Experiments 3 indicate that the nitrogen in food protein may in 

 part be replaced by ammonium salts. 



Copious water drinking increases the ammonia output. This fact 

 has been interpreted as indicating a stimulation of the gastric secretion. 4 



The acids formed during the process of protein destruction within 

 the body have an influence upon the excretion of ammonia similar to 



1 Magnesia -mixture may be prepared as follows: Dissolve 175 grams of MgSOi and 

 350 grams of NEUC1 in 1400 c.c. of distilled water. Add 700 grams of concentrated NHr 

 OH, mix very thoroughly and preserve the mixture in a glass-stoppered bottle. 



1 Ammoniacal silver solution may be prepared according to directions given on page 627. 



1 Grafe and Schlapfer: Zeit. physiol. chem., 77, i, 1912, experiments by Abderhalden in 

 same journal. 



4 Wills and Hawk: Jour. Am. Chem. Soc., 36, 158, 1914. 



