324 OUTLOOK FOR THE FUTURE 



conditions, as by the addition of stable manure or other plant and animal 

 residues, in order to favor the development of the antagonist. 



Thfc activities of antagonistic microorganisms are also utilized for 

 combating injurious insects and other lower animal forms destructive to 

 plants and to animals. Among the insects, the Japanese and other 

 Asiatic beetles have been treated rather successfully by the use of nema- 

 todes and certain specific bacteria. Extensive use has already been made 

 of these bacteria, by inoculating the soil with grubs heavily infected 

 with them. 



Comparatively little is yet known of the ability to control, by means 

 of antibiotic agents, diseases caused by protozoa, such as malaria and 

 trypanosomes, as well as virus infections. The hope of finding anti- 

 biotics active against such resistant diseases as tuberculosis has recently 

 gained much ground with the discovery that streptomycin has a re- 

 markable tuberculostatic effect and that it may find a place in the treat- 

 ment of certain forms of tuberculosis. 



These instances suffice to arouse hope that even greater progress can 

 be expected in the control of disease by utilization of the activities of 

 antagonistic microorganisms. So far, most energies have been directed 

 to the treatment of acute infections caused by bacteria. Less is known 

 of chronic infections. Whether or not man will ever be able to control 

 all diseases caused by the numerous microscopic and ultramicroscopic 

 forms of life through the utilization of the activities of antagonistic 

 microorganisms and antibiotics, he will have gained sufficient knowl- 

 edge from the mode of action of these organisms, and of the substances 

 produced by them, to justify further hope in the possibilities thus 

 opened. 



MODE OF ACTION OF ANTIBIOTIC SUBSTANCES: 

 A FIELD FOR THE PHYSIOLOGIST 



Finally, there remains the fourth important group of problems in- 

 volved in the study of antibiotics, namely, the mode of action of these 

 substances upon bacteria and other microorganisms. The fact that dif- 

 ferent agents vary greatly in their bacteriostatic and bactericidal action 

 upon different organisms is well established. A number of mechanisms 



