by by Professor Professor A. A. G. G. Everson Pearse Pearse The tide of of the Symposium, at at which the the papers which compromise this volume were presented, is of the utmost importance. It was not 'Fixation and Tissue Destruction' or 'Fixation 'Fixation and and Loss Loss ofTissue Components', Components', but but 'Fixation and and Tissue Tissue Preservation'. Historical Historical fixatives, fixatives, some some still still with with us us in the field oflight oflight microscopy microscopy after after over over 100 100 years, are are not not less less guilty guilty than than the the new new historical 'fixatives' of of ultrastructural ultrastructural practice practice some some ofwhich of which remove up up to to 60% 60% of the of the material material originally present in in the specimen and and convert the remainder into chemically inert products. There There must must be be few few hishemists hishemists who who do not not appreciate appreciate the great need need for for improve­ improve­ ments ments in in the the practice practice of of fixation, fixation, but but whence whence can can we we hopefully hopefully expect expect the arrival arrival of such such improvements? improvements— Apart Apart from from out out of the of the blue, or revolutionary, revolutionary, advances advances such such as as the advent advent of of glutaralde­ hyde, there are perhaps three principal sources.