THE OUTLOOK FOR THE FUTURE 263 



tyrothricin. It is known, for example, that various strains of B. mesen- 

 tericuSy B. mycoideSy B. subtiUsy and B. simplex are capable of produc- 

 ing antibiotic substances, some of which are markedly different chemi- 

 cally, biologically, or in selective activity. A more detailed study of these 

 organisms and the substances produced by them is bound to enlarge 

 greatly our knowledge of this group of chemical compounds and their 

 therapeutic potentialities. 



Of all the nonspore-forming bacteria possessing antagonistic prop- 

 erties found in soils and water basins, only two have been studied in de- 

 tail : Ps. aerugwosa has been utilized for the production of pyocyanase 

 and pyocyanin, and C. iodinum for the production of iodinin. It is 

 known, however, that a large number of other nonspore-forming bac- 

 teria are capable of producing a variety of antibiotic substances, the 

 chemical nature and biological activities of which are still but little 

 understood. 



Only very few of the antibiotic substances produced by actinomycetes 

 have so far been investigated, isolated, or concentrated j namely, ac- 

 tinomycetin, actinomycin, streptothricin, and proactinomycin. Even 

 these few substances, however, differ markedly in chemical nature and 

 in biological activity. In view of the fact that as many as 20 to 40 per 

 cent of all the actinomycetes are known to be capable of producing 

 antibiotic substances, many of which undoubtedly differ from those that 

 have already been isolated, the wealth of material that is awaiting in- 

 vestigation can only be surmised. Some of these possibilities have been 

 definitely indicated. Here belong the lysozyme-like agents discussed by 

 Russian investigators (507), micromonosporin which is active largely 

 against gram-positive bacteria, and streptomycin (795). The latter was 

 found, on the one hand, to resemble streptothricin in its chemical prop- 

 erties and activity in vivo, and, on the other hand, to differ from it in its 

 antibacterial spectrum. 



The production of antibiotic agents by fungi likewise has been but 

 insufficiently studied. The following pertinent facts may direct attention 

 to the many problems still awaiting investigation : 



(a) Some antibiotic substances, like penicillin, clavacin, and gliotoxin, are 

 produced by a number of different organisms; the nature of the or- 



