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MOLECULAR STRUCTURE IN PROTOPLASM 



O. L. Sponsler and Jean D. Bath 



Laboratories of Physical-Biological Sciences, University of California, 



Los Angeles 



The principal aim in the sciences is comprehension; often a 

 secondary aim is control; and the more fundamental the nature of 

 the comprehension, the more certain is prediction and control. 

 With ideas somewhat like these in mind about ten years ago, we 

 began to turn from the molecular structure of cellulose (1) to the 

 possibilities of molecular structure in the components of protoplasm, 

 with the intention of carrying the molecular viewpoint as far as we 

 were able up into the submicroscopic or colloidal range and further, 

 if possible, into the microscopic. 



With the realization that many vital activites, although not all 

 of them, may occur at the molecular level, we felt that attempts 

 which would elucidate molecular structure and spatial arrangements 

 would be worthwhile even though the results obtained were far 

 from either conclusive or complete. The structural goal towards 

 which we are striving is still very indistinct although the stepping 

 stones are surprisingly clear and well defined in many cases. It is 

 like climbing toward the top of a high mountain; we carefully pick 

 our steps that we may not stumble; we make false starts, often 

 finding the way blocked by a wall or a chasm, but consistently the 

 way leads upward, always intriguing, and keeping us wondering 

 what remarkable vista awaits at the top. 



The comprehension we desire is of protoplasm on a molecular 

 level, in the range of molecular dimensions. To attain this, famil- 

 iarity is necessary with atoms considered as small particles; with 

 groups containing a few atoms, small molecules; with large molecules 

 containing the principal features of many small molecules; with small 

 submicroscopic particles, and with large particles close to the range 

 of visibility. In all cases we think of them as endowed with definite 

 properties of weight and of spatial dimensions, such as shape and 

 size. In addition to these they have other properties which may be 

 described in a general way as attraction and repulsion. These 

 categories are somewhat clearer when we say that the molecules 



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