SONIC AND OSMOTIC EFFECTS ON VIRUSES 177 



alone is not sufficient to explain the results. Malkiel points out 

 that there must be a repetitive antigenic unit throughout the 

 virus which is probably quite small compared to the cross sec- 

 tional area of the virus and which becomes exposed on breaking 

 the virus. In addition, some steric hindrance to the attachment 

 of antibody must be removed when the rods are shortened. 



Antibody to sonic treated virus was also prepared by injecting 

 rabbits, and it was found that more precipitate was formed with 

 this also. This again argues for a simple repetitive unit. 



When the aggregated virus, prepared by incubation at the 

 isoelectric hydrogen-ion concentration, was used to combine with 

 antiserum, less precipitate resulted. This is not unreasonable, as 

 surface area becomes covered by aggregation, and the method of 

 reassembly probably squanders more area at the joints than is 

 needed by the normally attached virus. 



This idea, of a small antigenic unit, is excellently confirmed by 

 the deuteron bombardment studies described in Chapter 3 and 

 lends some confidence to the inferential methods used in virus 

 research. 



Osmotic Effects on Viruses 



Certain viruses will withstand suspension in a solution of high 

 molarity. Under such circumstances the virus becomes per- 

 meated, in at least part of its internal structure, with high-con- 

 centration solute among its molecules of water of hydration. The 

 osmotic pressure due to 4 J/ NaCl is 90 atmospheres, and if a 

 virus which has settled stably in such a solution is suddenly im- 

 mersed in nearly solute-free water, the osmotic pressure will 

 exert itself and an internal hydrostatic pressure will develop. In 

 a large enough virus, the force so produced may cause a rupture 

 at a weak internal point and so produce virus inactivation. 



This effect was discovered by Anderson (1949). He found that 

 T-2 phage was inactivated by the process of first immersing in 

 4il/ NaCl for a few minutes and then rapidly diluting the prepa- 

 ration with distilled water. He further showed that "ghosts," 

 which had the tadpole shape of T-2 phage, were present and that 

 they could absorb to the bacterium, although they were not in- 



