266 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1942 



virus shows strong double refraction of flow may prove of consider- 

 able importance in apparently unrelated fields, for if necessary the 

 virus could be prepared in pound lots or in larger amounts and used 

 to study the flow currents in apparatus such as pumps and hydraulic 

 rams or the nature of the flow when boats or projectiles move 

 through a liquid (pi. 3, figs. 1 and 2). Moderately concentrated so- 

 lutions of the virus, when allowed to stand, separate out into two 

 distinct layers, the lower of which is spontaneously doubly refracting 

 and the upper of which shows double refraction only when caused to 

 flow. Pellets of the virus obtained by ultracentrifugation are doubly 

 refracting. The strains of tobacco mosaic virus and cucumber mosaic 

 3 and 4 viruses have properties somewhat similar to those just de- 

 scribed. Latent mosaic virus of potato has a rodlike shape and ap- 

 pears to be even more asymmetrical than tobacco mosaic virus. The 

 layering phenomenon, the change in sedimentation constant with con- 

 centration, and certain of Bernal's X-ray studies, of Lauffer's ob- 

 servations on the electro-optical effect, and of Frampton's studies on 

 the thixotropic character of tobacco mosaic virus indicate that in 

 concentrated or moderately concentrated solutions there are inter- 

 particle forces which are effective over large distances. Although 

 in the past the existence of such long-range forces has been denied 

 for theoretical reasons, Langmuir and Levine independently have 

 recently shown that there are in fact good theoretical grounds for 

 their existence. The demonstration of the existence of forces acting 

 between molecules hundreds of A. units apart, and their acceptance 

 from the standpoint of theory alone, may prove of great importance 

 in connection with our theories of virus reproduction and other intra- 

 cellular events such as the duplication of chromosomes. 



The carbon, hydrogen, and nitrogen contents of bushy stunt virus 

 are about the same as those of tobacco mosaic virus. However, the 

 phosphorus and sulfur contents of 1.5 and 0.4 to 0.8 percent, respec- 

 tively, are considerably larger than those of tobacco mosaic virus. 

 Bushy stunt virus has a density of 1.35, a sedimentation constant of 

 132 X 10"^^, and a diffusion constant of 1.15 X 10"^ A molecular weight 

 of about 8 million and a particle diameter of about 26 ni/* may be cal- 

 culated from these constants. Solutions of bushy stunt virus do not 

 show double refraction of flow and the pellets obtained on ultracen- 

 trifugation are isotropic. The particles of the virus appear to be 

 essentially spherical in shape. The purified preparations are homo- 

 geneous when examined in the ultracentrifuge or the Tiselius electro- 

 phoresis apparatus (pi. 3, fig. 3) . Bushy stunt virus does not appear to 

 be susceptible to the peculiar aggregation which seems to be a charac- 

 teristic of the rod-shaped viruses and, unlike the latter, the sedimenta- 

 tion constant is almost independent of the concentration. Several 

 other viruses have been found to be essentially spherical in shape. 



