CHEMISTRY OF THE LEUCOMAINES. 285 



important part in the physiological function of the cell 

 nucleus, which, from recent observations, appears to be 

 necessary to the formation and building up of organic 

 matter. It is now known that non-nucleated cells, though 

 capable of living, are not capable of reproduction. We 

 must look, therefore, to the nucleus as the seat of the 

 functional activity of the cell — indeed, of the entire organ- 

 ism. Nuclein, the parent substance of adenine and guanine, 

 is the best known and probably most important constituent 

 of the nucleus, and as such it has been already credited 

 with a direct relation to the reproductive powers of the 

 cell. This chemical view has recently been confirmed by 

 Zacharias, who showed that chromatin of histologists is 

 identical with nuclein. Liebejrmastn has questioned nu- 

 clein as being the source of xanthine compounds, but in 

 this he is not supported by the mass of evidence. 



The method employed by Kossel for the preparation 

 of adenine, is as follows : The finely divided pancreatic 

 glands are heated to boiling, for three or four hours, with a 

 large quantity of dilute sulphuric acid (0.5 per cent, by 

 volume of concentrated acid), and the acid solution thus 

 obtained is treated with a slight excess of hot concentrated 

 baryta water. The excess of baryta is removed by carbonic 

 acid, and the solution is then filtered ; the filtrate is con- 

 centrated to a small bulk, about 100 c.c, rendered alkaline 

 with ammonium hydrate, and finally precipitated with an 

 ammoniacal solution of silver nitrate. The precipitate, 

 consisting of the silver compound of the xanthine bodies, 

 is partially dried by spreading over porous porcelain 

 plates ; then dissolved in warm nitric acid of specific 

 gravity 1.1, to which a little urea has been added to pre- 

 vent the formation of hypoxanthine should traces of nitrous 

 acid be present. The filtered acid solution, treated with 

 silver nitrate, on cooling, gives a deposit of the silver 

 salts of hypoxanthine, guanine, and adenine, which is fil- 

 tered oft and thoroughly washed. The adenine separates 

 out almost quantitatively if a little silver nitrate solution 

 is added. The filtrate contains any xanthine silver com- 

 pound that may be present. The washed precipitate of the 



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