40 THE CHEMISTRY AND PHYSICS OF THE CELL 



are still quite uncertain as to just the chemical differences that exist 

 between them. That there are differences is certain, and by means of 

 micro-chemical reactions, by comparing analyses of cells in which 

 nucleus or cytoplasm predominate, and by studying their phj'sico- 

 chemical relations to one another, we have arrived at more or less 

 tangible ideas on the question of the relation of the structural elements 

 of the cell to its compositi m. 



The Nucleus 32 



Although the nucleus presents morphologically a sharp isolation 

 from the cytoplasm, and displays equally sharp tinctorial differences, 

 it is probable that chemically the differences between nucleus and c^^to- 

 plasm are quantitative rather than qualitative. The characteristic 

 affinity of certain elements of the nucleus for basic stains depends 

 upon the presence in the nucleus of nucleoproteins in large proportion, 

 and to a limited degree nucleoproteins are characteristic of nuclei. 

 Their affinity for basic dyes depends upon the nucleic acid radical. ^^ 

 For example, the heads of spermatozoa contain nucleic acid bound to 

 simple proteins in such a way that it readily forms a salt or salt-like 

 combination with basic dyes, and so the sperm heads appear intensely 

 stained by alum-hematoxylin, etc. Ordinary chromatin threads of 

 nuclei appear to contain somewhat more firmly bound protein in their 

 nucleoprotein molecules, and hence stain less intensely than do the 

 spermatozoa heads, except when in karyokinesis, when the chromatin 

 nucleoprotein seems to approach that of the spermatozoa in avidity 

 for basic dyes. We also have nucleoproteins with the nucleic acid so 

 thoroughly saturated by protein that they do not stain at all by basic 

 dyes, and these seem to exist principally in the cytoplasm, and also to 

 form the ground-substance of the nuclei, occupying the spaces between 

 the chromatin particles (this achromatic substance of the nuclei is called 

 linin or plastin by some cytologists) . Besides the chromatin and the 

 nucleoli, there is a peculiar chromatophile substance, suspended in the 

 finer part of the nuclear structure in the same manner as the chro- 

 matin itself is in the coarser portions; this was called lanthanin by 

 Heidenhain,^'' and is probably similar to the substances also described 

 as parachromatin and paralinin. Undoubtedly the other forms of pro- 

 teins found in the cell, such as globulin, albumin, and nucleoalbumin, 

 exist both in the nucleoplasm and in the cytoplasm, the essential dif- 

 ference being that the proportion of nucleoprotein is nuich greater in 

 the nucleus. As nucleoproteins arc little alTectcd bj^ peptic digestion, 



32 Earlier literature bv Albrecht, "Pathologic der Zelle," Lubarsch-Ostertag, 

 Ergeb. der. allg. Pathol., 1899 (6), 1900: see also Kossel, Miinch. mcd. Woch., 1911 

 (58), 05. 



-■'■' Herwerdon (Arch. Zellforsch., 1913 (19), 431) found that the basophilic 

 gnmuUvs are disiutcgrated specifically by nuclease, supporting the view that they 

 are nucleic acid compounds. 



■>* Festschr. f. Kollikcr, 1892, p. 128. 



