548 WASTE-PRODUCTS 



or six years of age, but persists in the urine of girls until puberty. The 

 ingestion of creatine in children is also followed by an increase in the 

 creatine output in the urine. The adult has therefore acquired a power 

 of destroying or utilizing creatine which is imperfect in women and only 

 slightly developed in young children. 



Apart from the question of the nature of the tissues in which creatine 

 and creatinine originate we have to consider the problem of the chemi- 

 cal precursors or parent-substances from which they originate. A very 

 obvious possibility is that they may arise from Arginine. 



/NH 2 

 HN = C 



\NH.CH2.CH 2 .CH 2 .CHNH 2 .COOH 



by breaking the hydrocarbon-chain and methylation of one of the nitro- 

 gens in the guanidine nucleus. It has been stated that creatine may 

 arise from proteins in the autolytic decomposition of tissues in the 

 absence of bacteria but no other evidence of its formation from arginine 

 has yet been adduced. 



Creatinine is a reducing agent and decolorizes cupric hydroxide in 

 alkaline solutions, but does not precipitate cuprous oxide as the reduc- 

 ing sugars do. It is precipitated by Picric Acid, but if treated with 

 picric acid in alkaline solutions it yields a red coloration which turns 

 yellow upon the addition of acids (Jaffe's Reaction). If an alkaline 

 solution is treated with Sodium Nitroprusside the mixture turns ruby 

 red (Weyl's Reaction) and then yellow. If this yellow solution is treated 

 with excess of acetic acid and boiled, it becomes first green and then 

 blue (Salkowskfs Reaction). JafiVs reaction is utilized by Folin for 

 the colorimetric estimation of creatinine in urine. Creatine is esti- 

 mated by converting it into creatinine by boiling with dilute acid and 

 then reestimating the creatinine. 



Uric Acid is an exceedingly important constituent of the urine, since 

 it represents, in man, the end-product of the purine metabolism. The 

 average output per day on a mixed diet is 0.7 grams, and the ratio of 

 uric acid to urea varies between 1 : 50 and 1 : 70. 



Uric acid is derived from the Purine Bases by oxidation; it is 2, 6, 8, 

 trioxypurine : 



HN CO 



I I 



i i 



OC C NH 



HN NH/ 



It may be prepared synthetically from urea and glycocoll. On 

 heating in sealed tubes with hydrochloric acid, glycocoll, carbon 

 dioxide and ammonia are produced. It is capable of acting as a weak 

 acid and forms two series of salts, the Monourates, containing one, and 



