76 SCHLESINGER 



mulated information on the "intermediate" stages in the muhiphcation 

 of influenza virus, it is obviously of the greatest importance to re- 

 evaluate the meaning and the definition of viral activity, in particular 

 that of "inactivated" viruses which retain interfering ability. 



The other big question mark is the identity of the links which the 

 cell has to contribute to the viral reproduction. The problems have 

 been well stated by Luria in his Essay on Virus Reproduction, and they 

 are as essential to the problem of interference between animal-patho- 

 genic viruses as to the general problem of viral multiplication. 



LITERATURE CITED 



Anderson, K., 1942. Dual Virus Infections of Single Cells. Am. J. Path, 18, 577-583. 



deBurgh, P. M., Yu, P. C, Howe, C, and Bovarnick, M., 1948. Preparation from 

 Human Red Cells of a Substance Inhibiting Virus Hemagglutination. J. Exp. 

 Med., 87, 1-9. 



Delbriick, M., and Luria, S. E., 1942. Interference between Bacterial Viruses. I. In- 

 terference between Two Bacterial Viruses Acting upon the Same Host, and the 

 Mechanism of Virus Growth. Arch. Biochem., 1, 111-141. 



Fazekas de St. Groth, S., 1948. Destruction of Influenza Virus Receptors in the Mouse 

 Lung by an Enzyme from V. Cholerae. Austr. J. Exp. Biol, and Med., 26, 29-36. 



Francis, T., Jr., and Moore, A. E., 1940. Study of Neurotropic Tendency in Strains of 

 Epidemic Influenza. J. Exp. Med., 72, 717-728. 



Francis, T., Jr., 1947. Dissociation of Hemagglutinating and Antibody Measuring Ca- 

 pacities of Influenza Virus. /. Exp. Med., 85, 1-7. 



Friedewald, W. F., Miller, E. S., and Whatley, L. R., 1947. The Nature of Non- 

 specific Inhibition of Virus Hemagglutination. 7. Exp. Med., 86, 65-75. 



Gard, S., and von Magnus, P., 1946. Studies on Interference in Experimental Influ- 

 enza. II. Purification and Centrifugation Experiments. Ark. Kemi, Miner, och 

 GeoL, 24B, No. 8. 



Gard, S., von Magnus, P., and Svedmyr, A., 1947. Physi co-Chemical Aspects on In- 

 hibition and Interference in Experimental Influenza. Proc. IV Intern. Congress 

 Microbiol. Copenhagen, p. 301. 



Ginsberg, H. S., Goebel, W. F., and Horsfall, F. L., Jr., 1948. The Inhibitory Effect 

 of Polysaccharide on Mumps Virus Multiplication. J. Exp. Med., 87, 385-410. 



Ginsberg, H. S., and Horsfall, F. L., Jr., 1949. Concurrent Infection with Influenza 

 Virus and Muinps Virus or Pneumonia Virus of Mice (PVM) as Bearing on the 

 Inhibition of Virus Multiplication by Bacterial Polysaccharides. /. Exp. Med., 89, 

 37-52. 



Hardy, P. H., Jr., and Horsfall, F. L., Jr., 1948. Reactions between Influenza Virus 

 and a Component of Allantoic Fluid. J. Exp. Med., 88, 463-484. 



Henle, G., and Henle, W., 1946. Studies on the Toxicity of Influenza Viruses. I. The 

 Effect of Intracerebral Injection of Influenza Viruses. /. Exp. Med., 84, 623-637. 



Henle, W., 1950. Interference Phenomena between Animal Viruses: A Review. /. 



Immunol., 64, 203-236. 

 Henle, W., and Henle, G., 1943. Interference of Inactive Virus with the Propagation 



of Virus of Influenza. Science, 98, 87-89. 



