10 I. INTRODUCTION TO VIRUSES 



weight". At present, however, their inhomogeneity both in size and 

 shape appears to have become generally realized. 



All the particles present, regardless of their different properties, are 

 to be isolated by our chemical method and consequently virus prepara- 

 tions obtained by our method consist in most cases of particles of a 

 variety of sizes. It is, however, worthy of note that the particle size 

 seems to be governed mainly by the sort of cells from which the parti- 

 cles have been isolated. 



Thus, normal particles from E. coli were estimated to have an 

 average diameter of about 0.1 /{ in the dry state, whereas similar sized 

 particles were isolated from the bacterial culture lysed by a phage, that 

 is, the phage particles proved to have the size of the normal particles 

 (16). Again, vaccinia virus particles, obtained from the rabbit skin in- 

 fected with the virus, were found much larger in size than the bacterial 

 particles, being a little less than 0.3 /«, whilst the particles isolated from 

 the skin tissue rendered inflammatory by toxic agents other than the 

 virus possessed a similar large size. On the other hand, when isolated 

 from the rabbit testicles infected with the same vaccinia virus, the virus 

 particles were found to be of a much smaller diameter, being about 

 0.2 fx, which was proved in turn to be the size of particles obtained from 

 the normal testicles (17). 



In the case of vaccinia, however, some difference appeared to be 

 present in sizes between particles isolated from an infected rabbit 

 testicle and those from a normal testicle, but to a degree of insignifi- 

 cance. Also in the case of coli-phage, the difference due to phage 

 strains sometimes was found in particle size, though also usually 

 insignificant. 



The presence of the above mentioned remarkable difference in virus 

 size due to the difference in host cells seems to be of very importance in 

 the consideration of the virus nature. Besides us, some workers appear 

 to have already paid attention to this remarkable fact. For instance, 

 Bawden and Crook found that the size of potato virus X varies re- 

 markably with the kind of tissue extracts from infected plant, although 

 no great difference is detected in their infectivity (18). Levaditi also 

 stated that the poliomyelitis virus isolated from mice appeared much 

 larger than that isolated from monkeys (19). A strain of coli phage was 

 reported to exhibit different properties including particle size when 

 cultivated in different media (20), suggesting the presence of different 

 properties in bacterial protoplasm protein which varies with the media 

 in which they were cultivated. Moreover, mouse pneumonitis virus 

 preparations were found to show significant difference in size when 

 isolated from different sources, i. e., from mouse or rat lung or from 

 the yolk sack of the embryonated hen's eggs (21). 



