RADIATION AND VIRUSES 349 



acid (Dulbecco, 1950) and also liberate an agent, smaller than the virus 

 particles and separable by differential centrifiigation, which produces lysis 

 of the susceptible bacteria (Anderson, 1945). This lytic agent may or 

 may not be implicated in the normal lysis of bacteria infected with active 

 phage; the possibility of liberating active principles from virus particles by 

 means of radiation is, at any rate, suggestive of a new approach to virus 

 research. 



The situation described for the phages of the T group is by no means 

 unicjue; at least for influenza viruses, similar observations have been made 

 (Henle and Henle, 1947). Exposure to ultraviolet for progressively 

 longer periods of time eliminates, one after the other, all the properties 

 of the virus that can be studied. Reproductive ability disappears first, 

 followed by toxicity, which, according to Schlesinger (1950a), is a mani- 

 festation of an abortive infection in cells incapable of supporting full 

 reproduction of the virus. The ability of the virus to interfere with the 

 reproduction of another virus disappears next, followed by the immu- 

 nizing capacity for a susceptible host (which may have to do with both 

 antigenicit}^ and interfering ability). Hemagglutination — that is, the 

 ability to agglutinate red blood cells — is much more resistant and dis- 

 appears only after doses of radiation which probably disrupt the virus 

 particle. Complement-fixing antigens, mainly present in crude virus 

 preparations in the form of small "soluble" antigens, are greatly resistant 

 to irradiation. It is interesting that hemagglutination and complement 

 fixation should be the two most resistant properties of the influenza virus 

 since both of them can be found separated from virus activity in the 

 course of normal growth (Hoyle, 1948; Henle and Henle, 1949) and may 

 be in the form of immature elements of greater ultraviolet resistance. 



It may be noted that, to an inactive particle of influenza virus, radia- 

 tion can leave both the ability to agglutinate red blood cells and the 

 ability to be eluted from them enzymically, whereas heat, for example, 

 preserves the ability to agglutinate red blood cells but suppresses the 

 enzymatic elution. 



The separation of infectivity from the antigenic properties of a virus by 

 radiation is of fairly general observation. It has been proved for phages, 

 for plant viruses (which retain enough of their integrity to form the same 

 crystals or paracrystals as their active counterparts; see Bawden, 1950), 

 and for a series of animal viruses. The persistence of serological proper- 

 ties, however, may be limited to the effect of ultraviolet or of X rays 

 acting directly. In the case of papilloma virus, the indirect effect of X 

 rays gives a closer parallelism between the destruction of infectivity and 

 that of complement fixation than does the direct effect of X rays (Friede- 

 wald and Anderson, 1941). 



Because of the persistence of its antibody-stimulating ability, virus 

 which has been inactivated by radiation, in spite of some observation to 



