72 THE THEORY OF IONS 



Uric acid is the representative of the class. Its 

 origin in the animal organism, like that of urea, is 

 not settled beyond dispute. The urinary purins 

 find their origin in the decomposition of cell nucleins 

 and the free purin bases introduced in the food. 

 Knieriem* observed an increase in the excretion of 

 uric acid after administering amino-acids, e.g. 

 leucin, glycocoll, aspartic acid. Other authorities 

 agree that this may be one mode of origin. Whether 

 the amino-acids are decomposed by splitting off the 

 ammonia is unknown, but is considered very prob- 

 able. Minkowski found a large amount of lactic 

 acid in the urine of birds after extirpation of the 

 liver ; and considered that, at least in birds, the 

 uric acid is formed in the liver from lactic acid and 

 ammonia. Kowchski and Salaskinf also consider 

 they have proved that to be its origin, by administer- 

 ing lactate of ammonium to birds. Lactic acid, 

 C 3 H 6 3 , is hydroxy-acrylic acid or /3-hydroxy-pro- 

 pionic acid. It is one of the products of muscular 

 activity, and may arise from the decomposition of 

 amino-acids and members of the aliphatic series. 

 Uric acid is decomposable into urea and alloxan. 



When two molecules of urea are united by the 

 chain of an acid we have a diure'ide. Alloxan is 

 such a body, and is derived from urea and mesoxalic 

 acid. But mesoxalic acid only forms this link by 

 losing three atoms of oxygen (e.g. by OH ions acting 

 on it), whereby it becomes acrylic acid, one of 

 the aliphatic series, closely related to propionic 

 acid. Uric acid may therefore be regarded as com- 



* Zeit.fiir Biologie, xiii. 



t Zeit. Jiir Physiol.-Chem., xxxiii. 



