VIU PREFACE 



Although this new edition is concerned primarily with the 

 principles rather than the practice of microtechnique, I have 

 thought it right to come down to earth occasionally by giving 

 detailed practical instructions. The intention is to show the 

 student some of the applications of the principles. No attempt is 

 made, however, to provide a consecutive course of instruction 

 in practical microtechnique, for there are many excellent text- 

 books devoted to this subject.^^' ^^' i"' "^' "^' ^^^ 



When the first edition was written, I had already given nine 

 annual courses in microtechnique to students of zoology at 

 Oxford. Since then I have given twenty-four more. If one keeps 

 up with progress in a particular subject over a long period, it 

 becomes increasingly difficult to write a short book about it. One 

 can scarcely make a single statement without thinking of excep- 

 tions and reservations, or being conscious that an accurate 

 exposition would require longer treatment. The temptation to 

 equivocate is strong, but must be resisted. It will be realized that 

 my object is to transmit a general grasp of the subject — to put 

 the reader in a position to understand the complications when he 

 or she comes up against them. 



I hope that some readers may decide to pursue the subject 

 further in my larger book, Principles of Biological Microtechnique 

 (1958).^^ Those who have already seen the Principles may wonder 

 whether there is anything in the present book that might interest 

 them. The chief subject that is better treated here, I believe, is 

 the action of mordants. I have been carrying out research on this 

 since I wrote the Principles. I think it may be claimed that Chapter 

 9 of this book includes the first attempt to present a consistent 

 theory of mordanting in microtechnique, though certain parts of 

 the process have been admirably treated by Wigglesworth^^^ and 

 others. Much is known about the use of basic chromium salts as 

 mordants for azo-dyes in the textile industry, but this is a radically 

 different process. The discussion on fixative mixtures contains a 

 number of new ideas. There is also a clearer account of fixation 

 by mercuric chloride. In addition, the present book deals with 

 three subjects — embedding, mounting, and the structure of the 

 cell — that are only mentioned incidentally in the other. 



