AnfibJotic Research 171 



whereas the smaller viruses may have only a limited 

 metabolic activity and ofiFer correspondingly limited points 

 of attack for a chemotherapeutic agent. If, as appears to be 

 the case with bacteriophage, the metabolic reactions neces- 

 sary for the replication of the small viruses are in large part 

 mediated by the host cell itself, one must then hope that 

 there are specific metabolic functions which are more es- 

 sential to the virus than to the host cell, and can be blocked 

 by an appropriate agent. That agent has yet to be found. 

 (Some alternative possibilities and the complexities en- 

 countered in the experimental chemotherapy of viral in- 

 fection are discussed in Chapter 11.) 



ToxJcify of Anflbiofics 



Although the toxic reactions noted with every antibiotic 

 are usually minor and transient, in the rare patient they 

 may be serious or even fatal. Despite the increasing number 

 of such case reports, the pathogenesis of the serious hyper- 

 sensitivity reactions to penicillin, of the gastrointestinal re- 

 actions to the tetracyclines, and of the blood dyscrasias 

 sometimes observed with chloramphenicol, remains un- 

 explained and in large measure unexplored; as of now, the 

 occurrence of such reactions can be neither predicted nor 

 prevented. 



Developmenf of ResJsfance 



Much attention has focused on the problem of the emer- 

 gence of resistance to antibiotics. In my estimation, the 

 practical importance of the phenomenon has been greatly 

 exaggerated. True, staphylococci are now more resistant to 

 antibiotic therapy than they were ten years ago. There is 

 reason to believe that this represents not the development 

 of resistance in strains that were originally sensitive, but 

 rather the selective survival and multiplication, under the 



