CHAPTER I 



INTRODUCTION 



Cytochemistry is an almost undeveloped branch of biology. 

 It is only comparatively recently that a vigorous attempt has 

 been made to solve the problems which are involved in cytochem- 

 ical studies. Consequently, anything in the nature of a textbook 

 on cytochemistry is premature. There is an insufficient body of 

 agreed facts for it to be possible to write a textbook which would 

 set forth a body of methods and knowledge which would be 

 agreed to without question by the great majority of workers in 

 this field. I wish therefore to make it clear that this book is not 

 intended in any way as a textbook. It is very largely a record 

 of experiments which I have carried out myself, or which have 

 been carried out by other research workers with whom I have 

 been closely associated. Any of the individual methods given 

 here may well be superseded in a few years. I do, however, hope 

 that a good deal of what is recorded here may be regarded as in 

 the nature of a blueprint for future developments in cytochem- 

 istry. The general endeavour which is contained in this work, 

 namely, the development of rigorous methods, is a key matter 

 without which cytochemistry is a futile study. 



Cytochemistry is pre-eminently a field which calls for a team 

 of workers. The reason for this is that it demands a high stand- 

 ard of knowledge in each of the fields of biology, chemistry, and 

 physics. Unfortunately, many of the methods which have been 

 developed so far appear at first glance to be so simple that the 

 necessity for rigorous treatment has largely tended to be ignored. 

 There have, of course, been a number of outstanding instances of 

 compliance with the experimental criteria which are required: 

 this is obvious to all who know of the work of Feulgen, of Cas- 

 persson, or of Commoner. But the general tendency has been 

 to suppose that anyone who can cut a tissue section and make up 

 a standard solution is competent to carry out cytochemical in- 

 vestigations. Nothing could be further from the truth. Indeed, 



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