136 III. THE EVOLUTION OF VIRUSES 



III), but without producing the replica corresponding to the bacterial 

 template, so that haemolysin like lysozyme cannot be called a virus (12). 



3. Non-Pathogenic Viruses 



Bacteria, as a rule, undergo lysis when affected by a phage, but 

 lysis does not always follow phage infection. Some phage can infect 

 typhoid or coli bacteria without inducing lysis, though the phage can 

 multiply through the infection (13) (14). Bacteria infected with a 

 phage acquire the property to produce the phage like a genuine lyso- 

 genic strains ; thus certain bacteria at least can only be altered in 

 their character through the infection with a certain phage, without 

 being lysed. 



Since the multiplication of a virus consists in the replica formation 

 in the host cells, the cell disintegration must be only a result of the 

 multiplication, never an issue of necessity. The disintegration of 

 bacteria into minute particles in case of the phage infection may be 

 due to the destruction or the weakening of the mutual association of 

 elementary bodies of bacterial protoplasm caused by the structural 

 disturbance by the virus. Prior to the occurrence of lysis, bacteria 

 infected with phage, as is well known, may become indistinct in their 

 contour and swell up, a fact which is probably attributed to the ap- 

 pearance of lyotropic groups on the surface of elementary bodies as 

 a result of the structural disturbance, most probably of the unfolding 

 of the peptide chains. The disintegration may be thus caused by the 

 accumulation of water molecules among elementary bodies. If some 

 cells can endure such a change no lysis may follow. It is also con- 

 ceivable that the degree or the rate of the liberation of lyotropic 

 groups may vary with the kind of viruses which induce the change ; 

 thus certain host cells are disintegrated by some viruses while not by 

 others. 



It has frequently been noted that the virus multiplication is not 

 always accompanied by the manifestation of any pathological disorder. 

 The pathological disorder may be manifest when the changes lead to 

 the disintegration of the cells. Certain strains of influenza virus 

 multiply extensively in the mouse lung without producing pneumonia, 

 whereas a closely related variant may, under the same conditions, 

 produce pneumonic consolidation. Moreover, some strains of Coxackie 

 virus multiply to an equal degree in a number of organs but fail to 

 produce lesions except at certain specific sites (15). 



On the contrary in some cases pathological changes are most 

 remarkable, while virus multiplication scarcely occurs. Ginsberg (15) 



