OUTLOOK FOR THE FUTURE 321 



organisms; the nature of the organism often influences not only the 

 yield of the substance but also its chemical nature and its biological 

 activity. A number of other substances have been added to this list, 

 namely, fumigacin, viridin, penicidin, and others. 



(b) The mode of nutrition and the manner of growth of a single organ- 

 ism have often been found to influence the concentration and the na- 

 ture of the antibiotic substance, v^^hich may be formed in one me- 

 dium and not at all or in much lower amounts in another medium. 

 Some organisms are greatly favored in the production of antibiotic 

 substances by the presence in the medium of certain vitamin-like 

 complexes. Moreover, the formation of a substance is usually asso- 

 ciated with a certain stage of growth of the organism, since the sub- 

 stance is produced at one time and then rapidly destroyed, the range 

 of its accumulation often being very narrow. These facts point to 

 certain fundamental aspects in the physiology of the organism pro- 

 ducing the antibiotic substance that are still little understood. 



(c) Certain organisms, such as members of the Fusarium group, produce 

 bacteriostatic substances, the action of which, however, is rapidly 

 overcome by the bacteria. This points to problems on the stability of 

 the antibiotic substance and on the adaptation of bacteria to the sub- 

 stance. 



(d) Although it is known that certain yeasts produce antibiotic substances, 

 either of an adaptive or of a nonadaptive kind, very little is known 

 concerning the nature and mode of action of such substances. 



(e) Different strains of the same group of organisms, especially under 

 different conditions of culture, may produce the same type of sub- 

 stance which varies both chemically and biologically. This is brought 

 out by the formation of different penicillins. The same principle no 

 doubt holds for other antibiotics. 



These and many other problems are awaiting solution. The micro- 

 biologist is faced with a new field of research second only to that of the 

 very discovery of the causation of disease by microorganisms. 



THE OPPORTUNITY FOR THE CHEMIST 



'The chemist has been searching far and wide for new chemotherapeu- 

 tic agents. He has synthesized many thousands of compounds, only 



