402 PHYSIOLOGICAL CHEMISTRY 



struction of leucocytes. A well-marked increase accompanies leukemia. 

 Edsall and others have shown that the output of purine bases by the 

 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 Kriiger and Schmidt's method (see page 513), or Welker's method (see page 

 5i5). 



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 580) 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 



1 Magnesia mixture may be prepared as follows: Dissolve 175 grams of MgSO 4 and 

 350 grams of NH 4 C1 in 1400 c.c. of distilled water. Add 700 grams of concentrated NH 4 - 

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



2 Ammoniacal silver solution may be prepared according to directions given on page 593. 



3 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. 



