MOLECULAR STRUCTURE IN PROTOPLASM 



By O. L. SPONSLER 



DEPAETMENT OF BOTANY, THE UNIVEESITY OF CALIFOKNIA AT LOS ANGELES, LOS ANGELES, CALIF. 



During this conference on the cell and 

 protoplasm various excellent papers have 

 been presented which have given several 

 conceptions of protoplasm so far as consti- 

 tution is concerned: it was discussed first 

 as seen through the microscope; following 

 this various ideas were proposed introduc- 

 ing submicroscopic and molecular entities, 

 such as viruses, enzymes, hormones, and 

 vitamins which may exist within the proto- 

 plasm of the cell; but as yet no very tan- 

 gible picture of the protoplasm itself has 

 been presented, especially from a molecular 

 \iewpoint. What seems to be desirable and 

 what I shall attempt to present is a picture 

 which will bring together these molecular 

 and microscopic visualizations into a single 

 conception. 



Practically all of the picture is to be a 

 three-dimensional structure in the sub- 

 microscopic region closely associated with 

 molecular dimensions. The units or build- 

 ing blocks are of molecular and submicro- 

 scopic size, and in order to visualize them 

 we resort to models which are built to 

 comply with the known properties of these 

 units. 



Obviously the structure must be specula- 

 tive and hypothetical to a certain extent 

 but must have a foundation in experi- 

 mental fact. It is to be peculiarly free 

 from precursors, determiners, acceptors, 

 donors, and other indefinite substances 

 which are mostly names without physical, 

 molecular structure. The complexities, de- 

 tails, and known facts concerning proto- 

 plasm are so great that it has been neces- 

 sary in formulating the structure to resort 

 to the usual trick, so commonplace in bio- 

 logical fields and in other fields of science 

 although not always so obvious, of talking 

 in terms of genus or family while thinking 

 in terms of species. The result of this is 

 an ideal which is more or less representa- 

 tive of a large assortment of different spe- 

 cific forms. 



The picture we shall present, then, must 

 be considered as a first approximation, a 

 frame of a sort, which may be modified by 

 substitutions and additions where specific 

 demands require. It is an imperfect and 

 crude model which could not have been 

 made ten years ago, for our knowledge of 

 molecular structure and atomic dimensions 

 and properties were not then sufficiently 

 advanced. It may be a bit premature at 

 the present time, and we shall not be sur- 

 prised nor disappointed if new viewpoints 

 make considerable alteration necessary. 



To Ihose who have followed this series 

 of papers and discussions, wholly or in 

 part, it must have become evident that 

 protoplasmic material which could perform 

 in the various remarkable ways described 

 could do so only if it were organized struc- 

 turally along some definite plan. Perhaps 

 the plural would be better, for it seems 

 highly probable that no single plan could 

 account for all of the various phenomena 

 described by the writers. On the other 

 hand, there are certain features common to 

 the protoplasms of practically all organ- 

 isms, plant and animal. There must exist, 

 then, patterns within patterns. The ver- 

 satility displayed by protoplasms, speaking 

 in a general sense, seems far too great to 

 come within a single pattern, for directly 

 or indirectly we have ascribed to the living 

 protoplasm practically all of the processes 

 and activities which may be attributed to 

 living organisms. 



"Structure," in the sense of pattern, has 

 appeared time after time in these papers as 

 the theme around which a conception of 

 activities has been built. Structure and 

 organization, to our mechanical minds, re- 

 quire materials from which to be con- 

 structed ; and the conception of activities 

 demands a dynamic, a changing, moving, 

 active structure. The versatility required 

 seems to force complexity into the struc- 

 ture or, shall we say, demands many struc- 



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