OUTLOOK FOR THE FUTURE 323 



been established. It still remains to be determined whether this organ- 

 ism exerts a favorable effect due to its antagonistic properties or is only 

 another wound-infecting agent. 



Of particular importance is the development of the manufacture of 

 antibiotic substances. Largely because of the stimulus given by World 

 War II when the need for new antibacterial agents became very acute, 

 an intensive study was made of the practicability of utilizing some of 

 the agents already known, and search was made for new ones. Among 

 these, penicillin occupies a leading place. A large number of great con- 

 cerns in this country, in Great Britain, and elsewhere are engaged in the 

 manufacture of this drug by utilizing several strains of P. notatum and 

 P. chrysogenum. An intensive search for new strains resulted in the 

 isolation of cultures that have increased a hundred-fold the yield of 

 penicillin from the same lot of medium. The development of deep cul- 

 ture technique greatly reduced the labor involved. New agents capable 

 of inhibiting the growth of and destroying other pathogens resistant 

 to the action of penicillin have been isolated. Most significant of these 

 is streptomycin. 



The progress made in the isolation of antibiotic substances from many 

 microorganisms has not kept pace with their evaluation as chemothera- 

 peutic agents. In discussing antimicrobial agents of biological origin, 

 Dubos (200) emphasized that students of infectious diseases are pri- 

 marily concerned with the action of these substances upon certain strains 

 and stages of the parasites, with the mechanism of their action upon the 

 susceptible cells, and with physiologic and pathologic effects on the host. 

 Mcllwain (600), on the other hand, suggested that animal testing in 

 chemotherapy is not necessarily much nearer to the conditions under 

 which the drug will be finally used than are properly chosen in vitro 

 conditions i although in vitro testing does not reproduce all the condi- 

 tions of the normal environment of the parasite, it is less likely, under 

 present conditions of testing, to introduce new and unknown factors 

 than is testing in another host. The in vitro and in vivo studies of an 

 agent are considered as complementary. 



The utilization of fungi and bacteria against plant diseases has also 

 been variously attempted. The main difficulty involved is to estab- 

 lish the antagonist in the soil. This can be done by modifying soil 



