INTRODUCTION 



In these pages, the reader will find neither a treatise nor a textbook on 

 biochemistry, but a number of essays grouped around ideas of the unity and 

 diversity of organisms in the biochemical sphere, "The manifold and the 

 one" are eternal preoccupations of the human intellect, and we must not be 

 surprised that, from the time biochemistry has been able to gather together 

 a sufficient number of facts, the search for the lowest common denominator 

 of all organisms or a "unity of biochemical plan" has been confused in 

 many minds with the idea of a comparative biochemistry. The latter is a 

 problem which is perhaps more relevant to natural philosphy than to 

 scientific investigation, for we are becoming more and more aware of the 

 extreme diversity of biochemical function arising during cellular differentia- 

 tion in a single organism, as well as in the multiplicity of species and even 

 of individuals. The biosphere, by which we understand the total amount 

 of living matter, behaves like a chemist of a very special type. All the 

 organic compounds present in the many regions of the biosphere and re- 

 sulting from its biosynthetic activities have structures lying within 

 certain definite limits. The first part of this book provides a concise 

 catalogue of these structures but is not coincident with the contents of a 

 textbook of organic chemistry provided that the latter is not defined as it 

 was by Berzelius at the beginning of the 19th century, when he wrote that 

 organic chemistry is that section of physiology describing the composition 

 of living things and the chemical reactions going on therein. This defini- 

 tion of organic chemistry is no longer valid today; beginning with the 

 synthesis of a naturally occurring substance, urea, organic chemistry has 

 extended its domain to the synthesis of a tremendous number of non- 

 natural substances. One of the objectives of biochemistry is to define 

 and understand the nature of the collection of compounds composing 

 living matter and to distinguish them from those originating from non- 

 living sources and human inventiveness, all of which are described by the 

 broad generalizations of chemistry. 



The biosphere is not only a chemist of a special type, but also one of 

 great antiquity whose methods have been developed over a long period of 

 time since long before there were laboratories of organic chemistry, and 

 are of an efficiency far from being paralleled in these laboratories. This 

 point is developed further in the two essays which make up Parts 2 and 3 

 of this book with the intention of demonstrating the originality of this 

 organic chemist who has laboured since the dawn of time and comparing 

 his methods with those of the laboratory chemist. The essays making up 



