242 SOME ASPECTS OF CELL-CHEMISTRY AND CELL-PHYSIOLOGY 



change, some constituents being elaborated, others breaking down 

 into simpler products." 1 These conclusions established a probability 

 that the chemical differences between chromatin and cytoplasm, 

 striking and constant as they are, are differences of degree only ; 

 and they opened the way to a more precise investigation of the 

 physiological role of nucleus and cytoplasm in metabolism. 



3. Staining-reactions of tJie Nuclein-series 



We may now bring these facts into relation with the staining- 

 reactions of chromatin and cytoplasm when treated with the aniline 

 dyes. These dyes are divided into two main classes, 2 viz. the 

 " basic " anilines and the " acid " anilines, the colouring-matter playing 

 the part of a base in the former and of an acid in the latter. The 

 basic anilines (e.g. methyl-green, Bismarck brown, saffranin) are in 

 general "nuclear stains," having a strong affinity for chromatin, 

 while the acid anilines (acid fuchsin, Congo red, eosin, etc.) are 

 " plasma-stains," colouring more especially the cytoplasmic elements. 

 We owe to Malfatti and Lilienfeld the very interesting discovery 

 that the various members of the nuclein series show an affinity for 

 the basic dyes in direct proportion to the amount of nucleic acid 

 (as measured by the amount of phosphorus) tJiey contain. Thus the 

 nuclei of spermatozoa, known to consist of nearly pure nucleic acid, 

 stain most intensely with basic dyes, those of ordinary tissue-cells, 

 which contain less phosphorus, less intensely. Malfatti ('91) tested 

 various members of the nuclein-series, synthetically produced as 

 combinations of egg-albumin and nucleic acid from yeast, with a 

 mixture of red acid fuchsin and basic methyl-green. With this 

 combination free nucleic acid was coloured pure green, nucleins 

 containing less phosphorus became bluish-violet, those with little 

 or no phosphorus pure red. Lilienfeld's more precise experiments 

 in this direction ('92, '93) led to similar results. His starting-point 

 was given by the results of Kossel's researches on the relations of 

 the nuclein group, which are expressed as follows : 3 



1 It has long been known that a form of " nuclein " may also be obtained from the 

 nucleo-albumins of the cytoplasm, e.g. from the yolk of hens' eggs (vitellin). Such nu- 

 cleins differ, however, from those of nuclear origin in not yielding as cleavage-products the 

 nuclein bases (adenin, xanthin, etc.). The term " paranuclein " (Kossel) or " pseudo-nuclein " 

 (Hammarsten) has therefore been suggested for this substance. True nucleins containing 

 a large percentage of albumin are distinguished as nucleo-proteids. They may be split into 

 albumin and nucleic acid, the latter yielding as cleavage-products the nuclein bases. Pseudo- 

 nucleins containing a large percentage of albumin are designated as nucleo-albumins, which 

 in like manner split into albumin and paranucleic or pseudo-nucleic acid, which yields no 

 nuclein bases. (See Hammarsten, '94.) 



2 See Ehrlich, '79. 



3 From Lilienfeld, after Kossel, '92, p. 129. 



