PURIN BASES. 343 



of Minkowski (1898) render it very doubtful that a uric acid syn- 

 thesis occurs in mammals in a manner similar to that in birds. In 

 dogs the administration of urea, ammonium lactate and allantoin is 

 not followed by excretion of uric acid. Nevertheless it is obvious that 

 purin compounds are synthesized in the body out of the food sup- 

 plied. The growing cell can undoubtedly build up the purin molecule 

 out of simple material and is in no wise restricted to the preformed 

 nucleins or purins in the food. The amount thus synthesized in 

 mammals may be considered as not in excess of that necessary for 

 the purpose of the cells and hence the synthetic elimination of uric 

 acid is not recognized. In birds on the other hand it is conceivable that 

 the pronounced synthetic power of the liver is directed not at a 

 mere elimination of uric acid but rather at the formation of ante- 

 cedents (purins ?) which are utilizable by the cells and stored up 

 as nuclein. The supply of such antecedents being in great excess of 

 the actual needs of the economy leads to their oxidation and as a 

 result we have increased uric acid elimination which from this stand- 

 point would correspond to that of urea. The greater part of the 

 latter is believed to result from the breaking down of the circulat- 

 ing proteids when these are in excess of the needs of the tissues. 



When nucleinic acid is fed to mammals the amount of uric acid 

 eliminated is increased. The same is true as Taylor and others 

 have shown after a diet of sweet-breads which are rich in nucleins. 

 When, however, the actual amount of uric acid eliminated is com- 

 pared with the amount of nuclein present it is evident that by far 

 the greater part of the purin bodies is broken up and disappears. 

 Two explanations are offered on this point. In the first place it is 

 possible that the larger part of the purin bodies in nuclein is oxi- 

 dized direct into urea and only a small part goes to form uric acid. 

 Or, the second possibility is that the greater part is oxidized into 

 uric acid ; this in turn is largely broken down into urea, and only a 

 small portion escaping this cleavage appears in the urine. 



It is well known that uric acid when fed to mammals is broken 

 down and excreted as urea, allantoin (Salkowski), oxalic acid, 

 glycocoll and other products. If the amount of uric acid fed is 

 excessive allantoin can be detected in the urine, otherwise the cleav- 

 age is carried farther, as is seen in the fact that no allantoin can then 

 be isolated. The studies of Wiener (1899) have shown that certain 

 organs in the body when crushed may destroy while others appar- 

 ently make uric acid. Moreover the action of a given organ was 

 found to vary with the species of the animal. Thus, the liver, spleen 

 and thymus of beef were found to make uric acid whereas the liver 

 of dog and hog actually destroyed this substance. Again, the kidney 

 and muscles of the beef and horse were shown likewise to destroy 

 uric acid whereas the kidney of a dog did not. In these experiments 

 the antecedent of uric acid is undoubtedly nuclein since hypoxanthin 



