CHEMICAL RELATIONS OF NUCLEUS AND CYTOPLASM 337 



is coloured red, the albumin green, which is a beautiful demon- 

 stration of the fact that staining-reagents cannot be logically classified 

 according to colour, but only according to their chemical nature, 

 and gives additional ground for the viev/ that staining-reactions of 

 this type are the result of a chemical rather than a merely physical 

 combination. 



These results must be taken with some reserve for the following 

 reasons : Mathews ('98) has shown that methyl-green and other basic 

 dyes will energetically stain albumose, coagulated egg-albumin, and 

 the cell-cytoplasm in or after treatment by alkaline fluids ; while con- 

 versely the acid dyes do not stain, or only slightly stain, these sub- 

 stances under the same conditions. This probably does not affect 

 the validity of Heidenhain's results,^ since he worked with acid solu- 

 tions. What is more to the point is the fact that hyaline cartilage 

 and mucin, though containing no nucleinic acid, stain intensely with 

 basic dyes. Mathews probably gives the clue to this reaction, in 

 the suggestion that it is here probably due to the presence of other 

 acids (in the case of cartilage a salt of chondroitin-sulphuric acid, 

 according to Schmiedeberg); from which Mathews concludes that 

 the basic dyes will, in acid or neutral solutions, stain any element of 

 the tissues that contains an organic acid in a salt combination with a 

 strong base.^ Accepting this conclusion, we must therefore recognize 

 that, as far as the cytoplasm is concerned, the basic or " nuclear " 

 stains are in no sense a test for nuclein, but only for salts of organic 

 acids in general. In case of the nucleus, however, we know from 

 direct analysis that we are dealing with varying combinations of 

 nucleinic acid, and hence, with the precautions indicated above, may 

 draw provisional conditions from the staining-reactions. 



Thus regarded, the changes of staining-reaction in the chromatin 

 are of high interest. Heidenhain ('93, '94), in his beautiful studies 

 on leucocytes, has correlated some of the foregoing results with the 

 staining-reactions of the cell as follows. Leucocytes stained with 

 the Biondi-Ehrlich mixture of acid fuchsin and methyl-green show 

 the following reactions. Cytoplasm, centrosome, attraction-sphere, 

 astral rays, and spindle-fibres are stained pure red. The nuclear sub- 

 stance shows a very sharp differentiation. The chromatic network 

 and the chromosomes of the mitotic figure are green. The linin- 

 substance and the true nucleoli or plasmosomes appear red, like the 

 cytoplasm. The linin-network of leucocytes is stated by Heidenhain 

 to consist of two elements, namely, of red granules or microsomes 

 suspended in a colourless network. The latter alone is called " linin " 

 by Heidenhain. To the red granules is applied the term " o.xychro- 

 matin," while the green substance of the ordinary chromatic network, 



1 See below. ^ '98, pp. 451-452. 



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