104 PHYSIOLOGICAL CHEMISTRY. 



mulas of about the following character in nearly all cases : 

 C 40 H 52 N 14 O 2 5P 4 . These acids have not been obtained in 

 crystalline condition. They are but slightly soluble in cold 

 water, but soluble in weak alkali solutions when they form 

 salts. A number of salts of the heavy metals, which are insol- 

 uble in water, have been made and studied. When boiled in 

 aqueous or acid solution the nucleinic acids break up, yielding 

 finally the characteristic basic bodies, long known as the xan- 

 thine bases, phosphoric acid and certain carbohydrates. 



The nucleinic acids may be considered as esters of a complex 

 phosphoric acid derived from the condensation of four H 5 O 5 P 

 (true orthophosphoric acid) molecules. The various decom- 

 position products just referred to give some idea of the organic 

 groups replacing the hydrogen in the phosphoric acid. These 

 substituting groups need not always be the same, hence the 

 existence of different nucleinic acids. From the wheat embryo 

 an acid known as tritico-nucleinic acid has recently been iso- 

 lated and thoroughly studied. The formula determined from 

 a number of preparations was found to be, with great proba- 

 bility, C 41 H 61 N 16 O 31 P 4 . A silver salt of the composition 

 Ag C 41 H 55 N 16 O 31 P 4 was obtained from this, and on complete 

 hydrolysis it was found to yield one molecule of guanine 

 (C 5 H 5 N 5 O), one molecule of adenine (C 5 H 5 N 5 ), two mole- 

 cules of uracil (C 4 H 4 N 2 O 2 ), three molecules of a pentose 

 (C 5 H 10 O 5 ), phosphoric acid equivalent to four molecules and 

 other decomposition products. From nucleinic acids of animal 

 origin the xanthine (purine) bases have been found in other 

 proportions. The importance of these relations will appear 

 later when the origin and nature of uric acid (trioxypurine) 

 is considered. The uric acid of the urine probably comes from 

 the complete breaking down of nucleinic acids of cell struc- 

 tures, since both purine and pyrimidine derivatives are found 

 here, and both lead to uric acid. 



Nucleinic acids from yeast and other sources have found 

 some application in medicine. 



