26 



VIRUSES 



of a particle through a viscous medium involves in its hydrodynamic interaction 

 the solution as a whole rather than merely the solvent. Whether this hypothesis 

 is right or wrong makes relatively little difference. It should, in either case 

 serve as a stimulus for the further investigation of hydrodynamic interaction 

 and should, therefore, provide useful service to physical chemistry. 



Influenza Virus 



The size and shape of influenza virus has also been investigated in con- 

 siderable detail, A particular preparation was subjected to electron micro- 

 scopy, ultracentrifugation and viscosity studies by Dr. Stanley and myself. The 

 micrograph reproduced in figure 20 is of this preparation. 



FIGURE 20 - ELECTRON MICROGRAPH OP PR 8 liTPLUENZ^ 

 A VIRUS X12,000. (M.A. Lauffer and W.M. Stanley, J. 

 Exp. Med. 80, 531 (1944) ). 



The magnification is about 20,000. Prom the original photograph, whose magni- 

 fication factor was known accurately, it was possible to measure both the size 

 and distribution of sizes of the spherical particles. The mean diameter of 

 these spherical particles was found to be about II6 millimicrons. These parti- 

 cles are not all of exactly the ssune size. Kigure 21 shows the distribution of 

 particle sizes. 



? 14 



!3 12 

 S 10 



e 4 



i 2 



80 50 100 no 120 130 140 150 160 



Diameter in it 



FIGURE 21 - DISTRIBUTION OF DIAMETERS OF PR 8 INFLUETTZA A VIRUS PARTICLES 



A more or less continuous distribution can be seen. Prom this, it is possible 

 to calculate that the standard deviation of the distribution of particle dia- 

 meters is 1^% of the mean diameter. With the electron microscope it has been 

 possible to learn something of the external physical nature of Influenza virus 

 particles, but little was learned about the internal structure, ^or this, it 

 is necessary to turn to the ultracentrifuge . 



