CHAPTER 1 



The Structure of the Cell 



This book deals with the scientific principles underlying some of 

 the most ordinary processes of biological microtechnique : that is 

 to say, with the fixation, embedding, dyeing, and mounting of 

 small parts of organisms for subsequent study under the micro- 

 scope. It deals chiefly with the preparation of material for light- 

 microscopy; indeed, dyeing is not applicable if cells are to be 



examined with the electron-microscope (p. 85). 



The purpose of ordinary microscopical preparations is to 

 reveal minute structure. The study of this structure shows that 

 most organisms consist of cells and intercellular (or extra- 

 cellular) material; objects formed by the transformation of cells 

 (the red blood-corpuscles of mammals, for instance) often con- 

 stitute a third category of components. ^^ The primary com- 

 ponents are the cells, because the other constituents of the tissues 

 do not appear in their absence. The cells are, in fact, the proto- 

 plasm^^^' ^^^ or first-formed material, as indeed we can tell by 

 examining an early embryo; but since the expression first-formed 

 may suggest that something else formed them, it is more logical 

 to say that they are the plasson or formative material.^ ^ The 

 plasson constitutes the subject-matter of cytology, and this book 

 is concerned primarily (though not exclusively) with its fixation 

 and after-treatment in the routine processes of microtechnique. 



It would be a convenience if one could describe a 'typical cell' 

 and then show how this object was aff"ected by the ordinary 

 processes of microtechnique. Unfortunately there is in reality no 

 such object, though pictures of it appear in various textbooks. 

 Cells show great diversity of structure in relation to their particu- 

 lar functions. Some are so obviously untypical that they could 



B 1 



