668 PHYSIOLOGICAL CHEMISTRY. 



CN 2 H 4 O. When the two nuclei occur joined together into one 

 nucleus the latter is known as the purine-nueleus. Purine itself is a 

 hypothetical compound containing this nucleus. 



N C 



C 



u 



N/~1 XT /""I TT 



O JN =Url 



II II 



N x C C N. HC C NH. 



' U-> : 1J-N> H - 



Alloxan Urea Purine 



nucleus, nucleus. nucleus. 



By oxidation, or by replacement of hydrogen atoms in purine with 

 the radicals OH, NH 2 , NH, or by introducing the methyl group, 

 CH 3 , the different purine bases or allied compounds have been 

 formed. These bodies are also closely related to the vegetable bases 

 caffeine and theobromine, and also to uric acid, as shown in the fol- 

 lowing table : 



Purine 



Hypoxanthine (oxypurine) .... C 5 H 4 N 4 O 



Xanthine (di-oxy purine) ..... C 5 H 4 N 4 O 2 



Uric acid (tri-oxy purine) ..... C 5 H 4 N 4 O 3 



Heteroxan thine (methyl-xan thine) . . . C 5 H 3 (CH 3 )N 4 Oj 

 Paraxanthine (dimethyl-xanthine) \ . 



Isomeric with theobromine / ' ' M^CH^I^O, 



Caffeine (trimethyl-xan thine) .... C 5 H(CH 3 ) 3 N 4 O 2 



Adenine (amino-purine) ..... C 5 H 3 (NH 2 )N 4 



Guanine (amino-oxypurine) .... C 5 H 3 (NH 2 )N 4 O 



Carnine (dimethyl-uric acid) .... C 5 H 2 (CH 3 ) 2 N 4 O, 



Uric acid and the xanthine bases take up water and yield qualitatively the 

 same decomposition-products when treated with fuming hydrochloric acid 

 under pressure, viz., ammonia, carbon dioxide, glycocoll, and formic acid. 



Xanthine and hypoxanthine (sareine) occur generally together, 

 though in small quantities, in urine and in almost all tissues. In 

 larger quantity they are found in the meat-extracts. When pure 

 these bodies are colorless powders, almost insoluble in water, alcohol, 

 and ether. With acids they form crystallizable salts, and with silver 

 nitrate double compounds, which are employed in the separation of 

 the bases from fluids. 



Phosphocarnic acid is a glyco-nucleoprotein, occurring in muscle ; it yields 

 on hydrolysis succinic acid, carbon dioxide, phosphoric acid, a carbohydrate, 

 and carnic acid, a protein almost identical with peptone. It forms soluble 

 compounds with the alkaline earths, and also an iron compound (carniferrin) 

 soluble in alkalies ; these properties serve as a means to carry these metallic 

 compounds through the body. (Lacto-phosphocarnic acid is an analogous 

 compound found in milk.) 



