CHAPTER II 



THE SIZE OF VIRUS PARTICLES 



1. Relationship between the Kind of Host Cells and 

 the Size of Virus Particles 



A vast number of researches have been carried out concerning the 

 size of viruses, presumably mainly because viruses were believed to be 

 a type of microbes. If enzymes were similarly considered to be a kind 

 of microbes, profound attentions might have likewise been paid to their 

 particle, or molecular, sizes. However, of course, since no one ever 

 regarded them as microbes, little attention was paid to their sizes ; 

 nontheless, it is known that enzymes such as succinooxidase and 

 cytochrome exist in a particulate state like a virus (14), although 

 other enzymes such as pepsin, trypsin, and urease may be in a molecular 

 state of the globulin type. As will be stated later, there are other 

 enzymes or enzyme-like agents which should be regarded as having a 

 particulate nature as do viruses, indicating that the particulate nature 

 is never a characteristic feature belonging to viruses only. However, 

 on account of the combination of this particulate nature with other 

 characteristics which are the very image of microbes, the size of viruses 

 is apt to be regarded as being strictly specific to the sort of viruses. 



If virus particles are nothing but the protoplasm protein coagulated 

 into particles, it may be impossible for a virus to have always a uniform 

 size specific to the virus. It should be noted in this connection that 

 even protein molecules are known at present to have no uniform size. 

 Thus, recent electrophoretic studies have indicated that ^-lactoglobulin, 

 which had been regarded as an excellent example of a protein, pure in 

 view of their electrophoretic mobility, sedimentation constant, and solu- 

 bility, is polydisperse in a weakly acid solution, although appears 

 homogeneous at pH 8 (15). 



Since viruses were generally isolated by the application of centri- 

 fugal force, and since, as a rule, particles sedimentable at a given 

 revolution rate were separated and regarded as the only virus, it might 

 be a matter of course that the preparations thus obtained were composed 

 of similar sized particles. Thus in former days and occasionally even now 

 each kind of viruses is likely to be regarded as possessing its specific, uni- 

 form size, and some workers went so far as to calculate their "molecular 



