266 DIFFERENCES IN ANAEROB. FUNCTIONS 



cxpansa, where some fat is excreted but nevertheless large 

 amounts accumulate in the prog-lottids. Such an accumu- 

 lation is of no consequence since the proglottids of tape- 

 worms are only ephemeral structures. 



A different detoxication mechanism was suggested by 

 Harnisch (1939). According to him certain anaerobic 

 processes in insects may liberate oxygen which, in turn, 

 could be used to detoxicate poisonous substances. Fur- 

 ther experiments seem, however, necessary before the pos- 

 sible significance of this assumption can be judged. 



3. RE'LATION OF ANAEROBIOSIS TO OXIDATION- 

 REDUCTION POTENTIALS 



The problem of the relations of anaerobiosis to oxida- 

 tion-reduction potentials has been studied rather exten- 

 sively by the bacteriologists, and, for a theoretical discus- 

 sion, the reader is referred to a review by Clark (1934). 



Certain metabolic processes are directly dependent on 

 the attainment of a definite potential. For example, the 

 liberation of hydrogen by a bacterial culture is possible 

 only when the reduction intensity of the culture medium 

 reaches that of hydrogen at one atmosphere pressure; 

 some anaerobic bacteria indeed are known to exceed that 

 intensity, that is, to produce a ''hydrogen overvoltage" 

 and thus to liberate hydrogen (Clark, 1924). 



It is also a well-established fact that bacteria are able 

 to condition the oxidation-reduction potential of their me- 

 dia {cf., for summaries, Rahn, 1932 and Stephenson, 1939), 

 partly through their oxygen consumption, partly through 

 the elaboration of metabolic end products of low reduction 

 potential. (The latter mechanism is assumed when the 

 potential reached by the cultures is lower than that of 

 deoxygenated sterile controls.) 



With invertebrates, similar studies can be carried out 

 only in bacteriologically sterile cultures since it would 

 otherwise not be possible to distinguish between the action 



