268 DIFFERENCES IN A N 1 EROB, FT'NCTIONS 



The question then arises of tlic effect that the oxida- 

 tion-reduction potential of the medium has on inverte- 

 brates. Efimotf, Nekrassow and Efimoff (1928) report- 

 ed that the Eu of hay infusions changes from -322 mv. 

 shortly after the preparation of the infusions to +422 

 mv, ten months later. This change was probably due 

 primarily to bacterial activity. They further observed 

 that the appearance and disappearance of various pro- 

 tozoan species was most rapid during the periods of rapid 

 change in potential. 



Jalin (1933a) studied the growth rate of Chilomonas 

 in bacteria-free cultures in which definite potentials had 

 been established by the addition to the basic medium, of 

 H:.0o and of compounds containing the SH-radical. The 

 results suggested that the growth rate of the ciliates was 

 influenced by the potential, but the evidence was not 

 quite conclusive. Jahn (1933a, 1934) himself pointed 

 out that an alternative explanation could be found in a 

 possible influence of the various amounts of reduced 

 sulfur present in the cultures. 



Another interesting study is that of Jacobs (1941) 

 who investigated the oxidation-reduction potential of 

 pure cultures of bacteria in relation to the cultivation 

 of Endamoeha histolytica. He observed that excyst- 

 ment and growth of the amoebae occurred at potentials 

 of -114 to -150 mv., but that growth was more pro- 

 nounced in the range of -300 to -500 mv ; in other words, 

 this organism seemed to require, in culture, a rather 

 strongly reducing medium. Jacobs' results are in fair 

 agreement with the fact that Endamoeha histolytica u- 

 sually lives in surroundings with quite low oxygen ten- 

 sions. 



As to the influence of the oxidation-reduction poten- 

 tial of the surroundings on metazoa, we have the follow- 

 ing few data. Kollath and Erhardt (1936) studied the 

 survival in vitro of the fluke Opisthorcliis felineus in 



