KREATININ, XANTHIN BASES, OXALURIC AND OXALIC ACIDS. 483 



It is increased particularly by greatly augmented muscular activity, after the 

 ingestion of food rich in nitrogen. It is wanting in the urine of infants. 



Kreatinin yields an alkaline reaction, is readily soluble in water and in hot 

 alcohol, and it forms colorless, oblique rhombic columns. It combines with acids, 

 but also with salts. Kreatinin-zinc chlorid is prepared for the detection of krea- 

 tinin. 



Demonstration. A few drops of a slightly brown, watery solution of sodium 

 nitroprussid and then dilute sodium hydrate added to 5 cu. cm. of urine cause 

 a Burgundy-red color that soon disappears. Addition of acetic acid changes the 

 color to yellow. Acetone yields a similar reaction, though in the case of this 

 substance the red color becomes still darker, almost purple, after addition of 

 acetic acid. Acetone can first be driven off from the urine by boiling, and then 

 the reaction of kreatinin is certain. 



Xanthin-bases : Alloxuric Bases. Under the names xanthin-bases or nuclein- 

 bases, or alloxuric bases, are comprised a group of bodies, including xanthin, 

 hypoxanthin, adenin, guanin, carnin, which are related genetically to uric acid, 

 and, together with it, are also designated alloxuric bodies. The mother-substance 

 of all alloxuric bodies, including uric acid, is purin (C 5 N 4 H 4 ), from which are 

 derived: hypoxanthin, as oxypurin; xanthin, as dioxypurin; uric acid, as trioxy- 

 purin; adenin, as 6-aminopurin; guanin, as 2-amino-6-oxypurin. By the en- 

 trance of one methyl-group into the xanthin-molecule, there result the isomers, 

 i-methylxanthin, 3-methylxanthin, y-methylxanthin (heteroxanthin) . If two 

 methyl-groups enter, there are formed theobromin, paraxanthin, and theophyllin. 

 If 3 methyl-groups enter, caffein is formed. 



Salomon and Kruger found in the urine hypoxanthin, xanthin, adenin, hetero- 

 xanthin, paraxanthin, i-methylxanthin, y-methylguanin; and of the foregoing, 

 respectively, in 10,000 liters of urine, 8.5 grams, 10.1 grams, 3.5 grams, 22.3 

 grams, 15.3 grams, 31.3 grams, 3.4 grams. 



Alloxuric bases are prepared from the urine as combinations with silver or 

 copper, and these are decomposed by hydrogen sulphid. The crude bases, treated 

 with dilute hydrochloric acid, exhibit varying solubility. The vegetable alkaloids 

 of coffee, tea, and cocoa are the antecedents of heteroxanthin. Paraxanthin is 

 derived from caffein. Studies of the alloxuric bodies, therefore, are of value only 

 after protracted abstinence from the beverages named. 



Xanthin, C 5 H 4 N 4 O 2 , is present in small amounts only; according to E. Sal- 

 kowski, it may, however, under some circumstances, be as much as one-eighth 

 of the weight of uric acid. It is an amorphous, yellowish-white powder, quite 

 readily soluble in boiling water. It is said to be present in the urine in somewhat 

 greater amount after courses of treatment with sulphur, in leukemic patients and 

 in conjunction with nephritis in children. Rarely it forms urinary calculi. It 

 represents an intermediate link between sarcin and uric acid. Guanin and hypo- 

 xanthin can be converted into xanthin. In contact with water and ferments, 

 xanthin is transformed into uric acid. Evaporated with nitric acid, it leaves a 

 yellow stain that becomes yellowish red with potassium and violet red when 

 further heated. 



Hypoxanthin, sarcin, C 5 H 4 N 4 O, can be prepared in the form of needles or 

 exfoliating scales from meat, milk, bone-marrow, liver, blood from the cadaver. 

 It is present in normal urine in smaller amount. Hypoxanthin exhibits great 

 resemblance to xanthin, into which it can be transformed by oxidation. Hydrogen 

 in the nascent state conversely reduces uric acid to xanthin and hypoxanthin. 

 Evaporated with nitric acid, it yields a light-yellow stain, which becomes more 

 intense on addition of sodium hydrate, but not reddish yellow. It is more readily 

 soluble in water than xanthin, and a means of differentiating the two is thus af- 

 forded. Guanin is wholly insoluble in water. 



Paraxanthin has proved toxic in moderate amount to dogs. Rachford found 

 it in the urine in considerable amount in cases of severe migraine with convulsive 

 conditions. 



Oxaluric acid, C 3 H 4 N 2 O 4 , occurs in the urine in but small amount as an ammo- 

 nium-salt, is but slightly soluble in water and appears as a loose white powder. 

 Ammonium oxalurate can be prepared from uric acid. Perhaps there is a physio- 

 logical connection between uric acid and oxaluric acid. 



Oxalic acid, C 2 H 2 O 4 , occurs, though not constantly, as calcium oxalate, to 

 an amount varying from 10 to 25 mg. daily. It is recognizable from its envelop- 

 shaped clear octahedra (Fig. 153, J), which are insoluble in acetic acid; biscuit- 

 shaped or hour- glass shaped crystals (Fig. 159, c) are less common. The genetic 

 relation between oxalic acid and uric acid appears demonstrated by the fact that 



