CHAPTER 



A Critique of Cytochemical Methods 



Arthur W. Pollister 

 Department of Zoology, Columbia University, New York, New York 



Introduction. Lairs of absorption. Localization of substances in cells: Preservation 

 of intracellular substances in situ — Nucleic acid staining and tests — Protein staining 

 and tests — Ultraviolet absorption of nucleic acids and proteins. Quantitative micro- 

 scopical methods: Visual comparison — Photometric technique — Some errors of quantita- 

 tive microspectrophotometry — Quantitative applications, absolute and relative. References. 



1. INTRODUCTION 



The bulk of the extensive researches in cytology has been aimed pri- 

 marily at demonstrating the morphological features of the cell. By 1875 

 modern microscopes had become available which reached close to theo- 

 retical limits imposed by the properties of visible light, and within less 

 than two decades the application of this tool, in conjunction with an 

 increasing number of special microtechniciues for preparing cells for 

 examination, had demonstrated a wide diversity in intracellular mor- 

 phology and many striking correlations of cell structure with physiology. 

 From these studies the concept of the histological unit, the cell, emerged 

 with increasing clarity (Figs. 6-1, 2A). 



A similar morphological picture of most cell types could be drawn from 

 the researches of three-quarters of a century of cytology. Such a descrip- 

 tion, of course, is compfetely unsatisfactory from the standpoint of 

 intracellular biochemistry; indeed, it is merely an invitation to further 

 research which might lead to more nearly complete understanding of the 

 physiological processes by which such a cell can synthesize a secretory 

 granule or can elaborate the material to duplicate itself. One obvious 

 way in which to complete the picture is to attempt to determine the 

 chemical composition of the cell. To a cytologist this problem emerges 

 as one of demonstrating how the various substances, which biochemists 

 obtain by such procedures as extraction from minced organs, are dis- 

 tributed among the various visible cellular constitutents and in the 

 apparently structureless material which fills spaces between the iniclei, 

 mitochondria, granules, and other formed elements of the cell. Broadlj' 

 regarded, this appears to be the field of what has come to be called 



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