194 THE PHYSICS OF VIRUSES 



ing around the nucleic acid or nucleo])rotein internal structure. 

 Although these protein molecules carry the enzymes which cause 

 cell lysis among their number they do not cause lysis at once, for 

 many nearly complete individuals exist inside the bacterium a 

 minute or two before lysis occurs. 



Among the cell debris after lysis are units which can combine 

 specifically with antiphage so that exact assembly of all possible 

 virus components is apparently not a necessity, a rather welcome 

 lapse in an almost unbelievably efficient and coordinated process. 



The taking over of metabolism mentioned several times before 

 must include detailed molecular rearrangement, both on account 

 of the small size of serological unit which is remade in quantity 

 and because the bases present in virus nucleic acid have different 

 proportions from those in the bacterium. 



The 300 or so ])hage ])articles now enter a resting ])hase unless 

 more specifically suitable bacteria are present, in which case the 

 j)rocess goes on until all bacteria are lysed. 



This brief description is intended to be suitable for this book. 

 More can be learned from Luria's article in Viruses 1950. The 

 question now arises as to what kind of physico-chemical proc- 

 esses underlie this amazing biological feat. 



Description of a Virus 



From time to time in the previous pages we have drawn })ic- 

 tures of viruses in terms of certain pro])erties shown by the })ar- 

 ticular experimentation which we had just described. Each of 

 these pictures was useful in clarifying the conclusions gained 

 about virus structure, but none of them expressed in any detail 

 the known facts about viruses. 



We have detailed studies on two or three plant viruses and 

 several bacterial viruses, notably members of the selected T- 

 series of E. coll phages. In Figs. 8.2 and 8.3 we show pictures 

 which represent educated guesses at the structure of two plant 

 viruses, southern bean mosaic virus, and tobacco mosaic virus. In 

 Fig. 8.4 we show a bacterial virus which is T-1 phage with a dash 

 of the properties of T-2 to fill out the incomplete studies on T-1 . 



