Vlll - PREFACE 



could not participate in person. This spirit of responsibility made it possible 

 to assemble all manuscripts of the individual papers within three months 

 after the end of the Symposium. 



This Symposium has helped to establish several new concepts, most im- 

 portant, perhaps, that of presynaptic inhibition. During the extensive dis- 

 cussions it was recognized that it is not permissible to generalize observations 

 made on one organ and in one species as occurring in all members of the 

 whole phylum, since the diversity of mechanisms may be as great among 

 closely related species as it is among representatives of diflFerent phyla. On 

 the other hand, it became quite clear that all the different observations permit 

 general hypotheses of certain physiological phenomena, which are of value 

 in the understanding and the interpretation of functions occurring in any 

 given species. 



It is unfortunate that the extensive and most lively discussions cannot be 

 printed. No provision was made to record the arguments and, quite frankly, 

 the discussions would not have been as free and uninliibited as they were, 

 had everybody been conscious of the fact that his words would be recorded 

 and printed. 



Obviously, not all differences of opinion have been resolved to the satis- 

 faction of every participant. In so far the book does not represent a unified 

 system of hypotheses. Here the reader must make his own judgment on the 

 basis of the facts that are amply given in the various papers, and on the basis 

 of the criteria set down in several presentations. On the other hand, a study 

 of the discussions of the many diverse phenomena will reveal a remarkable 

 unity of concepts. It is indeed astonishing that the terminology used to 

 describe and analyze inhibition in such diverse systems as the vertebrate heart 

 and the crustacean stretch receptors is nearly identical, indicating a unity of 

 facts, perhaps not suspected by many. 



All participants deserve credit for their formal and informal contributions 

 to the success of the Symposium. Whoever was invited to the meeting was 

 asked to participate in the planning, and the whole conference developed 

 almost organically and without strains and efforts. Special thanks, however, 

 are due to Sir John Eccles and Professor Ragnar Granit. Without their early 

 encouragement and support, the Symposium would not have materiaUzed. 



On behalf of all participants, I wish to thank Dr. R. L. Fernald and Dr. 

 and Mrs. A. W. Martin for their hospitality at the social evenings, and Mrs. 

 Grace Y. Chapman, the Symposium Secretary, for her charming and con- 

 tinuous assistance in matters personal and ofiicial. 



The help of Sra. Marta Orrego de Sanchez in the preparation of the Index 

 is gratefully acknowledged. 



We are indebted to the publishers and their American and West Coast 

 representatives, Mr. D J. Raymond and Mr. D. Shearer, for their enthusiastic 

 co-operation. 



Seattle, Washington Ernst Florey 



