PREFACE 



'Wot I like in that 'ere style of writin',' said the elder Mr Weller, 

 'is that there ain't no callin' names in it.' There is plenty of 'callin' 

 names' in this book and it is doubtful if Mr Weller would have 

 approved of it. Many names are inevitable, even in a popular book 

 about the nature of life, and the writer's chief problem is to know 

 where to draw a line between what may be expected to be intelligible 

 to general readers and technicalities. I have tried to make the style of 

 this book reasonably simple while still maintaining a level of informa- 

 tion and comment which, I hope, will not be without interest to 

 students of science and also scientists who are not experts. No doubt 

 readers will find some portions more difficult than others, but no 

 harm will be done if they skip passages which they do not like. 



It would be impossible to give authority for all the facts quoted 

 without overburdening the text with references. Some indications as 

 to where further information can be found are given in an Appendix, 

 for those readers who would like to follow up particular subjects. The 

 text is also supplemented by an Appendix containing a collection of 

 chemical formulae of some of the compounds mentioned. 



In writing this book I have made use, when appropriate, of 

 passages from a previous book, Man is a Microcosm, which is now out 

 of print. But the scope of the present book is much wider, quite apart 

 from the fact that many parts of the subject have advanced radically 

 in the last few years. 



I am much indebted to Dr P. Rosbaud, who read the MS and made 

 useful suggestions, and for his friendly assistance. I am also grateful 

 to Miss Jill Emmerson, for coping with an untidy manuscript. 



London 

 July 20, 1958 



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