CHEMISTRY OF THE CELL NUCLEUS 209 



the constitution of the nucleic acid molecule, which may be 

 represented in the following way : 



OH — P— Sugar — Guanine 



I 

 O H — P — Sugar— Adenine 



OH — P — Sugar — Cytosine 

 ! 



OH — P — Sugar — Thymine 



That is, we have a chain of four atoms of phosphorus, each of 

 which is united on the one side to a hydroxyl (HO) group, and 

 on the other to a sugar (hexose) molecule. Each hexose group 

 is united further to a base, and thus the four bases enumerated 

 above are linked into the molecule. 



It is impossible to prophesy whether such a formula will 

 stand the tests of criticism and renewed experiment ; but at 

 any rate it appears that if we have not reached the last chapter 

 of this interesting series of researches, we must be somewhat 

 near the penultimate one. 



Let me now add a few sentences relating to a practical 

 application to which this increase of knowledge has led and 

 is leading. The harmfulness of excess of uric acid in the body 

 is now a matter of common knowledge, and although some 

 enthusiasts would try to make us believe that uric acid is 

 the source of every human ill, it cannot be denied that it is 

 an important factor in many ailments. Every piece of know- 

 ledge that leads to an elucidation of its origin in the body is 

 therefore a step in the direction of the ultimate cure of gout 

 and allied disorders. 



In birds, where uric acid is the chief final stage in nitrogenous 

 katabolism, and where it is discharged as a urate in their semi- 

 solid urine, a process of synthesis which occurs in the liver is 

 the mechanism of its formation. But this synthetic building 

 together of lactic acid and ammonia does not take place in the 

 mammal; in the mammal it has now been proved beyond question 

 that uric acid is formed by oxidation from the purine bases, and 

 so ultimately originates from the breakdown of nucleic acid. 



If we contrast together the formulae of two of these bases 

 with that of uric acid, the relationship is evident : 



Hypoxanthine C 5 H 4 N H 



Xanthine C 5 H 4 N 4 2 



Uric acid C i H,N 4 3 



14 



