PREFACE IX 



research scholar to obtain complete information. Every effort has 

 been made to see that names have been mentioned of the workers 

 who have important discoveries to their credit. 



Another attempt to solve the problem of the dual purpose of the 

 book is the use of large and small print. // must be particularly stressed 

 that the parts set in small type are not by any means considered less 

 important or interesting than those set in large type. On the contrary, 

 they frequently contain the discussion of problems of particular 

 interest for the research scholar, while those set in large type contain 

 the basic facts of primary interest for the student. 



A special difficulty has been the lack of a uniform, generally 

 accepted nomenclature. A questionnaire on nomenclature was sent 

 to some authorities working in the field to whom we are indebted for 

 letting us have their opinion. It is evident that this anarchy of 

 nomenclature is felt keenly, but that at present no possibility exists 

 of arriving at a generally accepted agreement. We hope that the 

 suggestions we have made will contribute to the solution of this 

 problem. Those who do not like some of the names we suggest may 

 consider them as shorthand symbols, the meaning of which has been 

 strictly defined in the various chapters. 



The period during which the book was written was a propitious 

 choice for the completion of the work, due to the pause in the publi- 

 cation of research papers during the war. The important literature 

 published up to July, 1946, has been included. In some cases, it was 

 difficult to secure copies of papers published during the war years in 

 countries of the European continent. Reprints kindly sent by 

 scholars, and particularly photocopies prepared by the Australian 

 Council for Scientific and Industrial Research and the Bibliofilm 

 Service of the United States Department of Agriculture, Washington, 

 have helped overcome this problem. Not all papers that might have 

 been of importance could, however, be read in full; some had to be 

 quoted from abstracts. 



Every effort has been made to bring the book up-to-date by adding 

 short footnotes in which important recent contributions have been 

 cited and shortly discussed. These additions include the period from 

 middle of 1946 to about June, 1948. We wish to thank the publishers 

 for the indulgence they have shown us by permitting these additions 

 at so late a stage of publication of the book. 



Our thanks are due to Dr. W. W. Ingram, Director of the Institute, 

 and to the authorities of the Royal North Shore Hospital, for pro- 



