x AUTODIGESTION OF NUCLEO-PROTEIDS 433 



xanthin-bases disappeared. Jones and Whipple finding guanin and 

 adenin, but no xanthin or hypoxanthin amongst the hydrolytic 

 dissociation-products of Hammarsten's a-nucleo-proteid prepared from 

 the pancreas, reasoned that autolysis must give rise to the same 

 products as does hydrolysis. 



Kutscher 1 in 1901 prepared from the thymus gland a product 

 which he called thymin, and this he believed to be contaminated by 

 traces of uracil (the constitutional formulae are given on p. 427). 

 Levene 2 in 1903 obtained uracil from autodigested pancreas, while 

 by the action of mineral acids on the pancreas there is produced 

 thymin. As Levene failed to find thymin amongst the products 

 of autolysis, he concluded that uracil is formed in place of thymin, 

 but did not say whether this result was due to the presence of trypsin 

 or to some special enzyme. 



Araki 3 showed in 1903 that an enzyme is contained in the 

 thymus, which converts a-thyrno-nucleic acid into the /^-variety. 

 This, however, is a purely hydrolytic process, for the same result may 

 be obtained with trypsin or with hot alkalies. Reh 4 believes also in 

 some causal connection between the presence of thymin and uracil 

 amongst the products of autodigested lymph-glands and the absence 

 of xanthin-bases. 



Iwanoff 5 discovered in 1903, in the moulds Aspergillus niger and 

 Penicillium glaucum, an enzyme capable of disintegrating the sodium 

 salt of thymo-nucleic acid into phosphoric acid and into xanthin- 

 bases, and called the enzyme 'nuclease.' He believes it to play 

 an important part during ordinary cell metabolism. 



Schittenhelm and Schroter 6 confirmed the view that putrefactive 

 bacteria in general, and the coli-bacillus in particular, are able to convert 

 one kind of xanthin-base into another kind ; and Walter Jones 7 then 

 showed that in autodigested thymus xanthin is formed at the expense 

 of guanin and adenin, i.e. that the amino- group of guanin must 

 become replaced by a hydroxyl group, while the conversion of adenin 

 into xanthin is brought about by the substitution of oxygen for the 

 amino-group and the replacement of a hydrogen-atom by a hydroxyl- 

 group. In both these cases ammonia is split off, and in the case of 



1 Kutscher, Zeit. f. physiol Chem. 34. 114 (1901). 



2 Levene, ibid. 37. 527 (1903) ; and the autodigestion of the spleen, ibid. 38. 404 

 (1903), and 39. 135 (1903). 



3 Araki, ibid. 38. 84 (1903). 



4 Reh, Hofmeister's Beitrage, 3. 569 (1903). 



5 Iwanoff, Zeit. f. physiol. Chem. 39. 31 (1903). 



6 Schittenhelm and Schroter, ibid. 39. 203 (1903). 



7 Walter Jones, ibid. 41. 101 (1904). 



2 F 



