VIRUSES, CANCER, GENES, AND LIFE 1 — STANLEY 361 



For a long time many investigators thought that the plant viruses 

 differed basically from viruses affecting animals and man. This idea 

 stemmed mainly from the fact that for 20 years all the crystallizable 

 viruses were plant viruses. This idea had to be relinquished two 

 years ago when my colleagues, Carlton Schwerdt and Frederick 

 Schaffer, obtained poliomyelitis virus, which is a typical animal or 

 human virus, in crystalline form. Since then at least one other ani- 

 mal or human virus has been crystallized and this is crystalline Cox- 

 sackie virus obtained by Doctor Mattern of the National Institutes of 

 Health. Hundreds of viruses are known and more are being dis- 

 covered every month; yet only a dozen or so have been obtained in 

 purified form. In view of the possibility that these may represent 

 the more stable and more readily purified viruses, one cannot be cer- 

 tain that a true picture of the chemical and physical properties of 

 viruses as a whole has been obtained as yet. However, I believe that we 

 have sufficient sampling to be significant for the purposes of the pres- 

 ent discussion for we already know that viruses may range from small 

 crystallizable animal, human, or plant viruses which are nucleoprotein 

 molecules, through intermediate structures consisting of nucleoprotein, 

 lipid, and carbohydrate, to large structures possessing a morphology 

 and composition similar to that of accepted cellular organisms. All 

 these diverse structures are bound together by one all-important prop- 

 erty, that of being able to reproduce their own characteristic struc- 

 ture when placed within certain living cells. They are all, in short, 

 by definition, alive. 



Now I am only too fully aware of objections that some may have 

 to considering a crystallizable nucleoprotein molecule as a living 

 agent. Some may feel that life is a mystery which is and must re- 

 main beyond the comprehension of the human mind. With these 

 I must disagree. Some may believe that a living molecule is contrary 

 to religion. Here again I must disagree for I see no conflict what- 

 soever between science and religion and I see no wrong in accepting 

 a molecule as a living structure. To many scientists the diverse ex- 

 pressions of chemical structure represent miracles, and our expanding 

 knowledge of the wonders of nature provides ample opportunities to 

 express our faith and only serves to make us full of humility. Some 

 may prefer to regard a virus molecule in a crystal in a test tube as a 

 potentially living structure and to restrict the term "living" to a virus 

 during the time that it is actually reproducing. I would have no 

 serious objection to this for I am reminded of the facts that certain 

 tapeworms a foot or so in length can live and reproduce only in cer- 

 tain hosts and that even man himself can be regarded as requiring 

 rather special conditions for life, yet no one objects to accepting man 

 and tapeworms as examples of life. I am also reminded that we are 



