Prefc 



ace \^ 



The principles of biological microtechnique may perhaps be re- 

 duced to one — the principle that when we make a microscopical 

 preparation of any sort, we ought to try to understand what we are 

 doing, for otherwise we shall examine an unknown object that has 

 been treated in an unknown way. A scientific outlook has been 

 introduced into certain branches of our subject, particularly histo- 

 chemistry, but there are others in which rule of thumb rules indeed. 

 One thinks at once of the most ordinary processes of the histo- 

 logical or cytological laboratory: of fixation, embedding, dyeing, 

 and mounting. Here the empirical outlook is often manifest, and 

 some workers are content to follow the recipe-book blindly, as 

 though a scientific result could be obtained by unscientific means. 



A very long book — and a very learned author — ^would be neces- 

 sary if the attempt were made to illustrate the principles of micro- 

 technique by a full consideration of all its branches. It seems best 

 to concentrate on the most familiar processes, so that the principles 

 may find most frequent application in practice. In fixation and in 

 dyeing the tissues are responsive : they react to what we do to them. 

 In embedding and mounting they are more passive, allowing us 

 to surround them with what we w^ill. I therefore choose fixation 

 and dyeing as being even more interesting than the other familiar 

 branches of microtechnique. I hope that a study of the principles 

 that should guide us in these branches may engender an outlook 

 towards microtechnique that will find application in a wider field. 

 This outlook is at least as necessary when tissues are prepared for 

 the electron microscope as in our more homely endeavours within 

 the realm of light. 



The book is addressed to research-workers, teachers, and 

 students in the fields of pathology, histology, cytology, zoology, 

 and botany. The primary intention has been to make it as useful 

 and attractive as possible to the consecutive reader, but certain 

 features have been introduced to help the casual inquirer. Thus 

 there are numerous cross-references and rather a lot of repetitions. 

 Three of the chapters (5, 6, and 9) can be used as though they were 

 parts of a work of reference. A full index is provided. 



vii 



