THE ANIMAL CELL. 47 



are more or less easily dissolved by alkalies ; in dilute mineral 

 acids they are insoluble or dissolve with difficulty. The nucleins 

 are not dissolved by pepsin-hydrochloric acid, or only slightly by its 

 continuous action. The nucleins containing albumin answer to 

 the biuret test and MILLON'S reaction. With dilute mineral acids 

 at ordinary temperature they give off (at least for nuclein from 

 yeast or yolk of egg) metaphosphoric acid. On boiling with 

 caustic alkali they decompose and alkali phosphates are formed. 

 On burning they leave an acid-reacting, difficultly-burnt coke which 

 contains metaphosphoric acid. On fusing with saltpetre and soda 

 they give alkali phosphates. 



To prepare nucleins from nucleoalbumins casein is the best ma- 

 terial to employ. This is first dissolved in water containing about 

 2 p.m. HC1, the filtered solution treated with pepsin and digested 

 at the temperature of the body. After a little time a precipitate con- 

 sisting of nuclein appears, which is purified by repeated solution in 

 water with the aid of the smallest quantity of alkali, and by repre- 

 cipitating with acid, washing with water, and extracting with alcohol 

 and ether. From cells or tissues first remove the chief mass of the 

 albumins by the artificial digestion with pepsin-hydrochloric acid, 

 digest the residue with very dilute ammonia, filter, and precipitate 

 with hydrochloric acid. This precipitate is now digested with 

 artificial gastric juice and treated as above described. In detecting 

 nuclein the same method is used, and the last product is fused 

 with soda and saltpetre, and phosphoric acid tested for in the 

 melted mass. Naturally the phosphate lecithin (and jecorin) must 

 first be removed by acid, alcohol, and ether respectively. No exact 

 methods are known for the quantitative estimation of the nucleins 

 in organs and tissues. 



Among the decomposition products of the nucleins the so- 

 called xanthin bodies are especially of great interest. Although 

 LIEBERMANN, in opposition to the views of KOSSEL, considers 

 these bodies not as real decomposition products of nuclein, but 

 only as admixtures, yet until this question is settled more defi- 

 nitely, and since the xanthin bodies stand in close relationship to 

 the cell nucleus, it is perhaps most proper to speak of these bodies 

 in connection with the cell nucleus and the nucleins. 



Xanthin Bodies. With this name we designate a group of 

 bodies consisting of carbon, hydrogen, nitrogen, and in most cases 



