Introduction 



Ahe topic of this symposium, initiated in and assigned to me by the 

 Council of the Society of General Physiologists, has the advantage that every 

 physiologist can identify himself with it and will be as nearly an expert as those 

 represented in the volume. Hence all will have the gratification of being able to 

 criticize the treatment, for despite the predominance of symposia on steady 

 state aspects of physiology, what lield or problem or level of functional biology 

 is without its conspicuous examples of abrupt onsets or sudden changes in rate? 

 Biologists and laymen have long recognized that life is characteristically just 

 one thing after another: fertilization, mitosis, induction, contraction, recep- 

 tion, infection, reproduction. But few are the cases where physiological analysis 

 has given insight into the mechanism of the trigger. Indeed what is a trigger? 

 The subtitle of this volume is an admission that, even after picking our examples 

 and formulating our own definition, analysis reveals apparent triggers are some- 

 times actually levers — though often coupled in a complex way, like the ac- 

 celerator of a car. 



The present assortment of physiologists, intentionally diverse, as explained 

 in the Preface, have undertaken to pioneer, without guideposts, in the hope 

 of being provocative. Unlike the usual symposium, the authors were not 

 familiar with one another's field. None could weave together the threads they 

 had in common. Each was urged in his own way and in the detail he saw fit to 

 come to intimate terms with the actual mechanism of his 'trigger.' The result 

 is bound to be a specialized treatment of a heterogenous group of fields and 

 obviously unity is not expected. The justification and the dividends are set 

 forth in Dr. Buck's explanation of the philosophy of the Society of General 

 Physiologists' symposia. Any new systematization, comparisons and contrasts, 

 principles or criteria must arise after the symposium and in the minds of those 

 readers willing to cross both the vertical lines dividing fields and the horizontal 

 lines between the levels of analysis. 



The symposium was held at Woods Hole, Massachusetts during the Society's 

 1955 meeting. As reported in Science (vol. 122, pp. 1098-1100) it included out- 

 standing contributions by Folke Skoog and Lawrence Blinks which rounded 

 out the botanical side, but which, to our regret, are not printed here. By special 

 invitation the papers of Jean Botts, J. B. Buck and K. S. Cole have been added 

 since the Woods Hole meeting. 



