

1 



THE NUCLEIC ACIDS 



Before we attempt to discuss the behaviour of the cell and of its 

 microscopically appreciable components, there should be given some 

 account of those macromolecules the changes in which, at a lower 

 order of magnitude, are now known to relate to the visible events 

 within the cell, and are believed in some way to initiate and govern the 

 course of the whole complex of biological events which results in the 

 production of two cells from one. 



HISTORICAL 



The history of this branch of biology is an interesting one, for it may 

 be said that it began in the seventies and eighties of the last century 

 with studies on the chemistry of the cell nucleus, which only in recent 

 years have been resumed. Then, as now, there are two general 

 methods which could be used for such investigations. Under the micro- 

 scope one can study the behaviour of cells and tissues towards stains 

 and reagents, or alternatively cell components such as nuclei can be 

 separated from gross quantities of tissue and then analysed in bulk by 

 chemical methods. 



By the eighteen-sixties the affinity of cell nuclei for colouring agents 

 such as carmine was well known (Mann,^ Baker^), and the recogni- 

 tion that the invariable presence of the nucleus pointed to its essential 

 role in the life of a cell led Miescher, a pupil of His, to attempt its 

 investigation by the second of these general methods, for which he 

 needed a source of one type of cell in large quantity.* He first used pus 

 from surgical bandages, plentiful in the pre-Listerian era, a material 

 from which, although nicht tadelfrei, Miescher found that he could free 

 the degenerating leucocytes, and after further trials could separate 

 these as we should now say, into nuclear and cytoplasmic fractions. 

 Miescher describes the isolated nuclei as 'vollkommen reinen Kernen, 

 mit glatter Contour, homogenen Inhalt, sharf gezeichnetem Nucleolus, 

 im Vergleich zur ihren ursprunglichen Volumen etwas verkleinert' 

 (Miescher^). From these isolated nuclei, Miescher proceeded to 

 prepare a substance which he termed 'nuclein' with stronger acidic 

 properties than any organic cell constituent then known, and which 

 was soluble in weak alkali, but not in dilute acid. It contained a high 



* An admirable account of Miescher's life and work is given by Greenstein.^ 



