CHEMICAL RELATIONS OF NUCLEUS AND CYTOPLASM 243 



Nucleo-albi(ijti)i (i % of P or less), 

 by peptic digestion splits into 



Peptone 



Nudein (3-4 % P), 

 by treatment with acids splits into 



Albumin 



Nncleic acid (9-10 % P). 

 heated with mineral acids splits into 



Phosphoric acid 



Nnclein bases 

 (adenin, guanin, etc.). 



i^A carbohydrate.^ 



Now, according to Ko.ssel and Lilienfeld, the principal nucleo- 

 albumin (nucleo-proteid) in the nucleus of leucocytes is micleo-Jiiston, 

 containing about 3 % of phosphorus, which may be split into a form 

 of nnclein playing the part of an acid, and an albuminoid base, the 

 histon of Kossel ; the nuclein may in turn be split into albumin and 

 nucleic acid. These four substances — albumin, nucleo-histon, nu- 

 clein, nucleic acid — thus form a series in which the proportion of 

 phosphorus, i.e. of nucleic acid, successively increases from zero to 

 9-10 %. If the members of this series be treated with the same 

 mixture of red acid fuchsin and basic methyl-green, the result is 

 as follows. Albumin (egg-albumin) is stained red, nucleo-histon 

 greenish-blue, nuclein bluish-green, nucleic acid intense green. " We 

 see, therefore, that the principle that determines the staining of the 

 nuclear substances is always the nucleic acid. All the nuclear sub- 

 stances, from those richest in albumin to those poorest in it, or con- 

 taining none, assume the tone of the nuclear {i.e. basic) stain, but 

 the combined albumin modifies the green more or less towards blue." ^ 

 Lilienfeld explains the fact that chromatin in the cell-nucleus seldom 

 appears pure green on the assumption, supported by many facts, 

 that the proportion of nucleic acid and albumin vary with different 

 physiological conditions, and he suggests further that the intense 

 staining-power of the chromosomes during mitosis is probably due 

 to the fact that they consist, like the chromatin of spermatozoa, 

 of pure or nearly pure nucleic acid. Very interesting and con- 

 vincing is a comparison of the foregoing staining-reactions with 

 those given by a mixture of a red basic dye (saffranin) and a green 

 acid one ("light green"). With this combination an effect is 

 given which reverses that of the Biondi-Ehrlich mixture ; i.e. the 

 nuclein is coloured red, the albumin green. This is a beautiful 

 demonstration of the fact that staining-reagents cannot be logically 

 classified according to coloin-, but onlv according to their chemical 



1 I.e., p. 394. 



