APPENDIX 4 



USE OF THE WORD 'CHROMATIN' 



In general, it is best to avoid words that are supposed to denote 

 chemical composition but stand outside the system of nomen- 

 clature adopted by chemists. It seems unlikely that anything is 

 gained by using such words as 'linin' and 'plastin'. A case can, 

 however, be made for the retention of the word 'chromatin'. 



This word was introduced by Flemming in 1880. It is commonly 

 stated to have been introduced by him in 1879, presumably be- 

 cause E. B. Wilson ^^^^ said so; but it does not occur in the papers 

 by Flemming quoted by Wilson in support of his contention. 



Flemming introduced it as follows. 



Tor further study of the phenomena of division, there is the 

 question of a shorter w^ord for what I have hitherto called the 

 "colourable substance of the nucleus". Since the expression 

 "nuclear substance" is obviously exposed to many misunder- 

 standings, I shall for the time being coin the word chromatin 

 for it. From this name no preconception ought to arise that this 

 substance must be a definitely constituted chemical substance, 

 remaining unchanged in all nuclei. Although this is indeed 

 possible, we do not yet know enough about the nuclear sub- 

 stances to assume it. This only should be denoted by the word 

 chromatin: that substance in the cell nucleus which takes up the 

 dye in the treatments with dyes known as nuclear colouring.' ^"^^^ 



Two years later he added these remarks : 



'The [nuclear] netw^ork owts its refractivity, the nature of its 

 reactions, and its remarkable affinity for dyes, to a substance 

 which, in consideration of the latter character, I have provision- 

 ally named chromatin.' He goes on to say that it may be the 

 same substance as nuclein. 'I retain the name chromatin', he 

 continues, 'until decision on this shall be given by chemistr}^ 

 and I denote by it, wholly empirically, "the substance in the cell 

 nucleus that takes up the colour in nuclear dyeing".' He re- 

 marks, 'As soon as anyone is able to say exactly what the 

 colourable substance in the nucleus is, in terms of chemistry, 



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