The subject of this year's Symposium of the Society of General Physiologists, 'Subcellular Particles,' was selected by the Council of the Society. In the organization of this symposium, the aim was two-fold: first, to bring to the attention of the variegated membership of the Society the most recent work of the foremost investigators studying subcellular particles; and second, to emphasize the structural aspects of subcellular particles as related to their function, especially with regard to the properties of the heterogeneous system created by the very presence of the particulate material within the cell. It would be presumptuous to say that these aims were achieved with any degree of success, especially in the case of the second part of the over-all aim, where a large area of ignorance faces the experimenter.
The post-war years will, I believe, be considered a 'Golden Era' in the biological sciences and certainly in the study of cell inclusions. Tremendous advances have been made in elucidating the various activities of subcellular structures, due primarily to advances in technology and the inspiration of new concepts and new information from allied fields, as microbiology. Thus improvements in, and the coordination of, techniques in ultracentrifugation, electron microscopy and micro. chemical analysis have made possible a more definitive correlation between the particles or the parts thereof and their activities within the cell. Likewise, new information about important biochemical substances, as the nucleic acids, have influenced the trend of thought as to the function of intracellular structures. Yet, essentially, this type of progress of knowledge in this field does not shed light on such questions as 1) why are structural units necessary at all, and 2) what effect does structure have on chemical or biochemical conditions and/or reactions within the cell?
However, certain consistent generalities can be observed as the result of the sharp attention paid to intracellular structures. For example, structures seem to be involved in those situations where the cell requires protection from disrupting agents which, nonetheless, the cell must include as a part of its over-all organization in order to maintain a specialized function. Thus enzymes which, if allowed loose in the cell, would cause autolysis would be included in this category. Several papers in this volume point to this aspect of cellular structure and function.
Structure also seems to be necessary in the general situation where synthesis of substances is taking place. Here, however, in spite of the speculations concerning 'templates' the situation is not so simple nor so clear that the conclusion can be stated with any finality. A third and what seems to be a most important requirement for structure within the cell is found in the case of cellular activities resulting . . .