Baitscll • The Cell as a Structural Unit 225 



among biochemists as to whether the istry of hfe to structural formations of 

 unit particles of the viruses and the incredible beauty and exactness, from 

 bacteriophages are enormous protein the diatom shell to identical twins, 

 molecules equipped in some way for Furthermore, each living cell, as it pc- 

 propagation by autocatalytic reactions riodically dixidcs by mitosis, reveals a 

 or whether they are elementary' living temporary stage of cr)stallinitv at the 

 units. Stanley, from his extensive levels of microscopic visibilitv with 

 studies on the viruses, has taken a po- both nuclear and cytoplasmic elements 

 sition which to some extent favors the united in the complete pattern. "Hie 

 view that viruses are living agents, protoplasm in a cell in the intcrmictic 

 though possibly of a retrograde nature, periods is not less uniform in its or- 

 Apparently the evidence at hand does ganization; the c\ toplasm and kar\o- 

 not afford indisputable proof that the plasm are only woven into an ultra- 

 virus particles are either living agents microscopic pattern of different design, 

 or non-living proteins. However, the The proteins of cell protoplasm, which 

 evidence is conclusive that the fune- are essential to the maintenance of life 

 tional characteristics of the tobacco phenomena, form a perfect whole; all 

 mosaic are "part and parcel" of the the molecules are associated to form 

 protein molecule. Thev reproduce, they a microscopically visible macromole- 

 adapt themselves to certain variations cule, the cell. 



in different t}'pes of living cells, ex- Geologists long held to the Catas- 



hibit "heritable" permanent changes trophic Doctrine, the primar)' assump- 



or mutations, and are destroyed by cer- tion of which was that "natural forces 



tain conditions fatal to living cells. were more active and powerful in the 



It has been extraordinarily difficult past geological ages than they are now; 

 for the cvtologist to get a clear vision that great convulsions of nature had 

 of the ceil as a structural unit because riven the crust asunder into valleys and 

 he has been blinded by the brilliance elevated other portions into moun- 

 of its functional features and also be- tains." But by the middle of the last 

 cause he has been unable to penetrate century the Uniformitarian School 

 through the ebb and flow of the hetero- gained the ascendancy, largely through 

 geneous mixture of complex organic the influence of Hutton and Lyell. Ae- 

 substances which are necessarily ae- cording to this view geological proc- 

 cumulated within the cell boundaries esses in past ages had never differed in- 

 to keep the "wheels of life turning." trinsically from those of the present 

 The behavior and appearance of proto- day. And why, we now ask, should it 

 plasm indicates superficially that it is ever have been thought otherwise since 

 an emulsion, but this is illus'or\'; there is the same primary' forces and elemental 

 an underlying ultramicroscopic sub- materials were at work? Clcarlv biology 

 stance— protoplasm itself— now re- at the middle of the twentieth century 

 vealed by use of the X ray and other is in much the same position as was 

 experimental methods, a substance geolog\^ a hundred years ago in failing 

 which is continuous and highly or- to observe that there is a Uniformitar- 

 ganized. ian Principle per\'ading all types of or- 



All protoplasmic phenomena have ganization whether in the inorganic 



their source in this ultramicroscopic realm or in the organic* 



organization from the complex chem- The basis of separation between life 



* There is a little bit of catastrophism, however, in the thinking of most 

 geologists. — Ed. 



