GENERAL CONCLUSIONS 171 



subject of oxidation-reduction potentials. An abundant oxygen supply is necessary 

 for penicillin production, which was originally carried out in surface cultures, but is 

 now effected in aerated tanks. The similarities in the chemical formulae of penicillin 

 and biologically important compounds such as glutathione suggest possible mechan- 

 isms of action. The mode of action of sulphonamide drugs suggests that preliminary 

 oxidation-reduction changes may be necessary, and the same holds with the organic 

 arsenicals, the use of which has been simplified recently by the development of 

 dithiols of the B.A.L. type. 



A useful adjunct to electrode potentials for the study of biological oxidation- 

 reductions is found in polarography, which is of value in some systems with unstable 

 potentials and which are not completely reversible. Once the current flowing in 

 the system is measured it is possible with the Polarograph to obtain information 

 concerning the amount of an oxidation-reduction system present as well as its 

 qualitative nature. Substances present in minute amount may sometimes be detected 

 polarographically. 



We begin to realise the important part that the study of electrode potentials 

 may play in the explanation of bacterial problems and in the scientific development 

 of bacteriology. The introduction of pH measurements has led to considerable 

 improvement in bacterial technique, and it seems probable that electrode potential 

 studies will play an important part in elucidating problems of bacterial behaviour. 

 Such advances in bacteriology have preceded advances in other realms of biology 

 where the investigator has to deal, not with many cells of the same type, but with 

 cells of countless different kinds. A fuller understanding of unicellular behaviour 

 and its variations must assist the solution of the more complex problems. A striking 

 example of this has been the contribution of bacteriology to the study of the vitamins 

 during the past fifteen years and the development of microbiological methods of assay. 



It appeared to be the function of the nineteenth century to observe the simplicity 

 and unity of natural phenomena ; the twentieth seems rather to discover the 

 complexity and intricacy of the pattern. 



Closer understanding of the processes of metabolism and inheritance should now 

 lead to a rational approach to their control and to the mitigation of suffering due to 

 malnutrition, to infection, organic disease and perhaps old age. It may first be 

 necessary, however, for man to differ from other organisms and avoid competitive 

 inhibition. 



The biologist has long studied living organisms as wholes and will continue to do so 

 with ever-increasing interest. But these studies can tell us nothing of the nature of the 

 "physical basis of life,'' which no form of philosophy can ignore. It is for cheynistry 

 and physics to replace the vague concept of "protoplasm'' — a pure abstraction— by 

 something more real and descriptive. I know of nothing which has shown that current 

 efforts to this end do not deal with realities. It is only necessary for the biochemist ta 

 remember that his data gain their full significance only when he can relate them with the 

 activities of the organism as a ichole. He shoidd be bold in experiment but cautious in. 

 his claims. His may not be the last word in the description of life, but without his help 

 the last word will never be said. — Hopkins (1931). 



