PYRIMIDIN GROUP. 419 



photungstic acid. Inasmuch as Levene obtained uracil, CJ3.JSf>^, 

 in a similar auto-digestion of pancreas it may be that Kutscher's 

 body has a simpler formula than that given above and moreover it 

 may be related to, if not identical with, uracil. Its behavior to 

 silver is very much like that of thymin. 



The pyrimidin bodies may be obtained by the hydrolysis of pure 

 nucleinic acid but the better procedure is to separate them from the 

 hydrolytic products of the original tissue or material. The method 

 perfected by Jones is especially useful for this purpose. He em- 

 ployed the testicles of the herring from which the protamin had 

 been previously removed with an acid. This material was mixed 

 with 20 per cent, sulphuric acid and the mixture was autoclaved for 

 2 hours at 150°. This heating completely destroys the adenin but 

 is without effect on the thymin. After removal of the humus sub- 

 stances by filtration, powdered barium hydrate is added till a slight 

 but distinct alkaline reaction is obtained. The precipitate of barium 

 sulphate is filtered off and thoroughly washed with boiling water. 

 The combined filtrates are then concentrated so that for each 100 g. 

 of dry testicles there is 600 c.c. of liquid. 



A preliminary test is now made to ascertain the exact amount of 

 silver nitrate necessary. For this purpose, a small but known 

 amount of the liquid is taken and after slightly acidulating a 2 per 

 cent, solution of silver nitrate is added from a burette till a drop of 

 the liquid added to an excess of baryta water yields a yellow and not 

 a white precipitate. The amount of silver solution necessary for 

 portions of 500 c.c. of the liquid can then be calculated. 



The original liquid is then slightly acidulated with nitric acid 

 and divided into portions of 500 c.c. each. To each of these the 

 requisite amount of silver nitrate solution is then added. After 

 removal of the precipitate, the filtrate is rendered slightly alkaline 

 with baryta. This precipitate is washed by decantation and finally 

 drained over a pump. It is then decomposed with hydrogen sul- 

 phid, under pressure. The united filtrates on evaporation yield 

 crystals of thymin. These are decolored with charcoal and recrys- 

 tallized from hot water. In the case of herring testicles the yield 

 of thymin is about 2 per cent. 



It has already been pointed out that the pyrimidin bodies may be 

 considered as antecedents of the purin bodies formed in the animal 

 organism or more correctly as cleavage products of the latter. The 

 relation of the pyrimidin and purin bodies can best be shown by 

 equations representing the synthesis of uric acid. Behrend and 

 Eoosen prepared uric acid by combining urea with a pyrimidin 

 body — iso-dialuric acid. 



