154 Perspecfives in Microbiology 



susceptible cells (23, 30). The available evidence indicates 

 that the compound inhibits the intracellular reproductive 

 process. But there is as yet no indication of the means by 

 which this is accomplished. To inhibit reproduction after 

 a virus, or part of it, has entered a cell is not readily 

 achieved. This objective has been realized with chemical 

 substances in only a few instances, but these seem of suffi- 

 cient importance to warrant further work in this field. 



Mechanism of Virus Reproduction 



Inhibition of virus reproduction by chemical substances 

 might be achieved more readily if the mechanism were 

 fully understood. Because this phenomenon is an intracel- 

 lular process inseparable from the life of the cell, it has 

 not been possible to distinguish clearly between the role 

 of the virus and that of the cell. With bacteriophages, 

 large strides have been made recently, and it now appears 

 that the reproductive process involves a number of discrete 

 steps. Current theory holds that phage particles do not 

 enter bacterial cells as intact entities; that their nucleic 

 acids and genetic determinants do gain entry; that certain 

 components of the new particles are produced separately; 

 and that after assembly into mature particles these leave 

 the cell at the time of lysis (25, 26, 31, 40). This complex 

 process can then be repeated in series. 



With animal virus reproduction the present situation is 

 far less advanced. There is no good answer to the simple 

 question: do animal viruses multiply themselves, or are 

 they reproduced by the infected cell? Quantitative and 

 kinetic studies, as well as investigations with the electron 

 microscope, have not excluded the possibility that the mul- 

 tiplication of animal viruses may be formally similar to 

 that of microbial species which multiply intracellularly. 

 The rate of appearance of new virus particles after an ap- 

 propriate latent or lag period appears to be logarithmic in 



