PREFACE .IN certain respects the plant alkaloids rank among the most interesting of naturally occurring substances. Por the most part they are of very complex structure, so that the determination of their constitution and the discovery of methods of producing them synthetically offer attractive problems to the chemist and though a great deal has been accomplished, much still remains to be done in this direction. Their mode of origin and their function in plants are still unknown, and these two questiom, with the more important one of correlating the structure of the alkaloids with their physiological action, form still almost untouched fields for combined work on the part of physiologists and chemists. Many of the alkaloids are of great importance in medicine, and the manufacture of these alkaloids and of products containing them constitutes important branches of the fine chemical industry. In compiling this volume the author has kept in view these various aspects of the subject, and the articles on all the more important alkaloids describe not only the properties and the chemistry of these products, ut also their occurrence, methods of estimation, and physiological action. In most cases the original memoirs have been consulted and references to these are given in foot-notes, but for descriptions of the physiological action of the better-known alkaloids Professor Cushnyys Textbook of Pharmacology and Therapeutics has been largely utilised. The chemical nomenclature and the systeni of abbreviations used are, with a few unimportant exceptions, those eii ployed in the Abstracts published by the Chemical Society of London, with which most English-speaking chemists are familiar. For much laborious work in checking formulz and references and in reading proofs the author is indebted to Mrs. Henry, R. A., B. Sc. Lond., and to Miss A. Holmes, B. A. Lond.. INTRODUCTION PYRROLE GROUP PYRIDTNE GROUP ALI AT, I, OT DS WITH DIHETEROCITCLIC NUCLEI QUINOLTNE GROIJP 1,5 OQUINOLINE GROUP GLYOXALINE GROUP PURINE GROUP ALKALOIDS DERIVED FROM ALIPHATIC AMINES ALKALOIDS OF UNKNOWN CONSTITUTION APPENDIX-RECENT WORK ON ALKALOIDS INDEX INTRODUCTION THE word alkaloid was at first used to describe all organic bases, including the natural alkali-like substances which occur in plants. At the time this name was introduced comparatively few of these latter substances were known, and these were all alike in possessing basic properties and in exhibiting physiological activity. These two characteristics, in conjunction with their complex structure, have made it possible until recently to regard the natural alkaloids as forming a well-differentiated group of chemical compounds, but recent work has tended to render indistinct the border lines between this and other groups. On the one hand such simple basic substances as ammonia and methylamine, and on the other substances that contain nitrogen and are yet acidic rather than basic, have been found in plants. And, again, complex substances closely related to typical alkaloids and which must be regarded as belonging to the class of alkaloids, though they have no marked physiological action, nre lrno vn... --This text refers to the Paperback edition.