CHAPTER I 

 VIRUS PARTICLES 



1. The Key to Solving the Riddle of Life 



There may be no riddle so fascinating and so difficult as that of 

 life. Around us, — on the land, in the sea, under the ground, or in the 

 air, life is wriggling, jostling, thronging in every possible shape. What 

 is living ? Even to think about this question is the very manifestation 

 of life itself. A great number of inquisitive human beings have tried 

 and even now are trying to pierce its mystery. Viruses are the key to 

 solve this fascinating riddle. Without this key it may be impossit)le 

 to open the mysterious chamber of life and, accordingly, to find out the 

 nature of viruses is indispensable for the solution of the riddle. 



It has long been Icnown that the majority of infectious diseases are 

 caused by microorganisms such as bacteria and protozoa. There are, 

 however, many infectious diseases not originated by microorganisms 

 observable under the ordinary microscope, and such infectious diseases 

 appear to be rather more numerous. Among these are common cold, 

 measles, and mumps, the diseases by which almost every one of us is 

 affected. Smallpox, influenza, trachoma, yellow fever, poliomyelitis, 

 many types of encephalitis, rabies, etc., are also counted among them. 

 Not only human beings but also many other creatures, for instance, 

 domestic animals, insects, and vegetables, are also infected with them. 



The agents producing such diseases are now known to pass through 

 bacteria-proof filters, and are called filtrable viruses or shortly viruses. 



The characteristic features of viruses are firstly their too small size 

 as compared with other pathogenic microbes, and secondly their in- 

 ability to grow in vitro with ordinary bacteriological method; for their 

 multiplication are needed always living cells, in which only they can 

 grov/. For the multplication, however, usually a virus needs a certain 

 kind of living cells ; that is, certain cells of a certain creature are 

 necessary for the multiplication. This fact is of great importance, 

 since it reminds us of the relation between an enzyme and its substrate. 

 Thus, the relationship between a virus and the cells in which it can 

 grow appears similar to that betv/een diastase and starch, or between 

 pepsin and protein. These enzymes, however, cannot multiply by 

 affecting the respective substrate in contrast to viruses which can mul- 



