THE STRUCTURE OF VIRUSES 



135 



ation may prevail at the other extreme of 

 size. Neither the cell nor the atomic theory- 

 should be handicapped by a reference to 

 the living state, but should be utilized only 

 to define certain accepted orders of struc- 

 ture. It should also be recognized that 

 there may be such a gradual transition be- 

 tween these accepted orders of structure 

 that the designation of intervening entities 

 as molecules or as cells becomes one merely 

 of personal preference. The nature of the 

 bonds between units within cells, as well 

 as the nature of the bonds which hold to- 

 gether the large nucleoproteins, requires 

 much more investigation before they can 

 be completely understood. However, at 

 the present time there is no reason to be- 

 lieve that they differ in any fundamental 

 respect from the forces already known to 

 exist in atoms and molecules. We must, 

 therefore, recognize a continuous series of 

 structures ranging from atoms and mole- 

 cules, through the viruses to living organ- 

 isms. The secret of life is not bound up 

 exclusively with the latter, for although I 

 quite agree with the statement that Conklin 

 made in the first paper that there is life 

 in organization, I do not think that organi- 

 zation, that life, suddenly disappears below 

 the cell. A hydrogen atom represents or- 

 ganization, a protein molecule tremendous 

 organization, and in man a still higher 

 degree of organization is represented. The 

 expression of the structure or organization 

 encountered in man is, in reality, but 

 little more surprising or mysterious than 

 that encountered in atoms and molecules. 

 Consider the vast array of expressions 

 involved in going from carbon and hydro- 

 gen atoms, two pairs of which may form 

 the gas acetylene, to the related molecules 

 of benzene, napthalene, anthracene, di- 

 benzanthracene, the carcinogenic hydro- 

 carbons, the sex hormones, ergosterol, 

 vitamin D and perhaps those interesting 



materials which Dr. Harrison mentioned, 

 the mammalian organizers. These are not 

 complicated structures, for their molecular 

 weights are less than 500, yet they exhibit 

 an amazing range of activities. It is not 

 surprising that this range should be 

 widened in the case of proteins, whose 

 molecular or particle weights are measured 

 not in hundreds but in thousands and in 

 millions, to include activities that are in- 

 distinguishable from those which have been 

 regarded as characterizing living organ- 

 isms. There is, therefore, a continuum 

 from what have been called living organ- 

 isms to what have been called molecules. 

 We should recognize that both may, in fact, 

 be regarded either as organisms or as 

 molecules, that they differ only in the de- 

 gree of organization, and that the terms 

 living and non-living may be applied only 

 to entities at the two extremes, in much 

 the same way that the terms acid and alka- 

 line are used to describe hydrogen-ion 

 concentration. No difficulty is encountered 

 so long as the degree of life, or of inani- 

 mateness, or of acidity or of alkalinity is 

 sufficiently great, but in each instance there 

 is an intermediate zone where it becomes 

 impossible to effect an exact definition 

 based on such terms without the use of 

 some arbitrary point of division. With 

 the realization that there is no definite 

 boundary between the living and the non- 

 living, it becomes possible to blend the 

 atomic theory, the germ theory, and the cell 

 theory into a unified philosophy, the es- 

 sence of which is structure or architecture. 

 The chemical, biological, and physical 

 properties of matter, whether atoms, mole- 

 cules, germs, or cells, are directly depend- 

 ent upon the chemical structure of the 

 matter, and the results of the work with 

 viruses have permitted the conclusion that 

 this structure is fundamentally the same 

 regardless of its occurrence. 



