NITROGENOUS WASTE-PRODUCTS 



551 



and Izar have shown that if an extract of liver which has completely 

 destroyed a given sample of uric acid in the presence of oxygen be 

 excluded from oxygen, the uric acid is gradually reformed. This is 

 what one would expect if we had here to deal with a reversible oxidation. 

 The curious feature of their results is, however, that the addition of 

 allantoin had no effect upon the production of uric acid, appearing to 

 indicate that the production of allantoin was not an intermediate step 

 in the resynthesis. 



The power of uricolysis is absent from the tissues of man and the 

 chimpanzee a fact which would have gladdened the heart of Huxley, 

 could he but have known it. All other mammals, so far as we know, 

 contain uricase in their tissues. The following results, cited after 

 Hunter and Givens, show the relative proportions of uric acid and 

 allantoin in the urine of various mammals. The "Uritolytic Index" 

 is the proportion, expressed as a percentage of uric acid, which has 

 been converted by the animal into allantoin. 



Orders and species. 

 Marsupialia: 



Opossum . 

 Rodentia: 



Rabbit 



Guinea-pig 



Rat . . 

 Ungulata: 



Sheep . 



Goat . 



Cow . 



Horse . 



Pig. . 

 Carnivora : 



Raccoon 



Badger 



Dog . 



Coyote 

 Primates : 



Monkey . 



Chimpanzee 



Man , 



Total purine 



nitrogen, 



gms. 



. 0.04 



0.2 to 0.6 

 1.0 

 8.0 

 1.6 

 0.3 



. 0.25 

 O.ltoO.3 

 . 0.15 



. 0.045 

 ... 

 . 0.2 



Percentage of purine-allantoin- 

 nitrogen. 



Allantoin. Uric acid. 

 76.0 19.0 



91.0 

 93.7 



64.0 

 81.0 

 92.1 

 88.0 

 92.3 



92.6 

 96.9 

 97.1 

 95.6 



66.0 

 2.0 



6.0 

 3.7 



16.0 

 7.0 

 7.3 



12.0 



1.8 



5.4 

 1.9 

 1.9 

 2.6 



8.0 

 90.0 



Bases. 

 6.0 



3.0 



2.7 



20.0 



12.0 



0.7 



0.5 



5.8 



2.0 

 1.2 

 1.3 



1.8 



26.0 

 8.0 



Uricolytic 

 index. 



79 



95 

 94 

 96 



80 

 92 

 93 



88 

 98 



95 

 98 

 98 

 97 



89 

 

 2 



Allantoin has been isolated by Hunter from the blood of the ox, pig, 

 horse and sheep, but could not be detected in the blood of man. 



It is not by any means certain, however, notwithstanding the 

 inability to convert uric acid into allantoin, that the tissues of man 

 cannot destroy uric acid in some other manner. Thus, Taylor and 

 Rose fed a human subject for three days on a diet very low in purines, 

 namely milk, eggs, starch, and sugar. For three days following, a 

 part of the protein, namely three grams per day out of a total of ten 

 was given in the form of "sweetbread" nitrogen (sheep's pancreas). 

 For four days succeeding this twice as much "sweetbread" nitrogen 

 was given, namely six out of ten grams, and this was succeeded by a 



