DIFFERENCES IN ANAEROB. FUNCTIONS 267 



of the test animals and that of the bacteria. Jahn (1935), 

 using sterile cultures of Chilomonas paramaecium, a nor- 

 mally aerobic organism, observed that the Eh of the me- 

 dium decreased from the second day after inoculation for 

 a iDeriod of several days and then rose again to almost the 

 original level. Thus the curves resembled those found 

 with cultures of aerobic bacteria. In this case the oxygen 

 consumption of the protozoa present in various numbers 

 at different times and the diffusion of oxygen into the me- 

 dium are probably sufficient to explain the observed 

 changes, there being no necessity of assuming the produc- 

 tion of reducing substances. 



Organisms better adapted to anaerobic life than Chi- 

 lomonas would probably produce lower potentials. It 

 would, then, be of particular interest to study the time- 

 potential curves in pure cultures of Trichomonas foetus. 

 This organism elaborates an inflammable gas which may 

 be hydrogen (Andrews and von Brand, 1938). In con- 

 formity with the findings on bacterial cultures, pro- 

 nounced changes in the oxidation-reduction potential 

 should be expected. As Clark (1924) remarks: *'It is 

 extremely difficult to conceive of molecular oxygen play- 

 ing any part in the activity of a cell that is producing a 

 hydrogen overvoltage and tearing to pieces by reductive 

 action materials which resist strong chemical reducing 

 agents." Applied to the present case this would mean 

 that once hydrogen production begins, the molecular 

 oxygen that may still be in the medium would play no 

 further role. (When oxygen is present at the tension 

 of the atmospheric air, however, it is being utilized by 

 Trichomonas, as Riedmueller (1936) has demonstrated.) 



In nature, inorganic constituents, and especially the 

 bacterial flora present in almost any habitat will be much 

 more potent than the metabolism of the invertebrates 

 in influencing the oxidation-reduction potential of the 

 surroundings. 



