296 LECTURE XIII. 



kowski, 1 who showed that when a dog was fed on material rich in purine 

 bases, such as thymus or pancreas, the amounts of allantoine eliminated 

 appreciably increased. Cohn 2 found that the administration of hypo- 

 xanthine to this animal had the same effect. Mendel and White 3 have 

 proved that intravenous injection of uric acid into cats and dogs, as well 

 as the injection of salts of nucleic acids, caused an increase in the allan- 

 toine elimination. Wiechowski 4 has furnished a better proof that uric 

 acid is decomposed into allantoine. He succeeded in showing that in 

 surviving beef-kidney and dog's liver, uric acid is changed quantitatively 

 into allantoine. This shows one way in which uric acid may be decom- 

 posed, but it does not necessarily follow that in the decomposition of uric 

 acid allantoine is formed in every case; perhaps the latter is further 

 decomposed into urea and glycocoll, and it is quite possible that normally 

 the decomposition of uric acid may follow an entirely different course. 

 On the other hand, we can hardly assume that the uric acid is all 

 decomposed in one way. It is conceivable that, for example, a part is 

 decomposed with the intermediate formation of glycocoll, while another 

 part gives rise to allantoine. 5 



This would give us a clear conception of the formation of uric acid in 

 mammalia. It can undoubtedly be traced to the degradation of nuclein 

 substances, and finally to the purine bases. It has never been decided 

 whether in birds and reptiles (animals in which, as we have seen, the uric 

 acid in its entire significance and formation takes the place of urea) a part, 

 if only a very small part, is formed in the way we have just indicated. It 

 is hardly to be doubted that entirely analogous processes take place in the 

 organisms of birds and reptiles. Similarly we have no reason for denying 

 that a synthetic formation of uric acid may also take place 'in the tissues of 

 mammals. 



Before considering the behavior of the remaining cleavage-products 

 of the nucleic acids in the animal organism, we must pay some attention 

 to the purine bases appearing in urine. We have already mentioned, 

 that, for example, in vigorous muscular activity, such large amounts of 

 purine bases are transmitted to the blood that the purine content of the 

 urine is increased. The animal cells do not have time to convert these 

 bases into uric acid. 



Purine bases are constantly present in the urine, some of which are to 

 be regarded as direct decomposition products of the nucleic acids, while 



1 O. Minkowski: Zentr. innere Med. 19, No. 19 (1898). 



3 T. Cohn: Z. physiol. Chem. 25, 507 (1898). 



8 L. B. Mendel and B. White, Am. J. Physiol. 12, 85 (1905). 



4 Wilhelm Wiechowski: Hofmeister's Beitr. 9, 295 (1907), 10, 247 (1907.) 



5 It is interesting to know that allantoine has been found in the bark of tree- 

 branches and in buds. Cf. E. Schulze and J. Barbieri: Ber. 14, 1602 (1881); J. 

 prakt. Chem. 26, 145 (1882); Z. physiol. Chem. 11, 420 (1886). 



