AEROBIC FERMENTATIONS 169 



trary, parasitic worms or free-living animals which had 

 undergone a period of oxygen deprivation were treated in 

 the same manner, the entire oxygen consumption (para- 

 sitic worms) or the post-anaerobic excess oxygen con- 

 sumption (free-living animals) was largely eliminated 

 by washing, but could be restored by the addition of 

 cell-free body fluid to the cellular suspension. These 

 observations indicate, then, that this type of oxygen 

 consumption (Haruisch's secondary aerobic processes) 

 is due to enzymes located not within the cells but in the 

 body fluids surrounding them. 



These differences are indeed very interesting and it 

 would be desirable to extend such investigations to or- 

 ganisms that, in respect to their normal oxygen supply and 

 their ability to live anaerobically, occupy intermediate po- 

 sitions between Ascaris and typically aerobic animals. 

 Trichinella and Eustrongylides larvae might be favor- 

 able objects. Harnisch (1937a) himself considers it pos- 

 sible that at least some parasites (for example, Bothrio- 

 ceplialus bipunctatus) may still possess vestiges of pri- 

 mary aerobic processes. In this connection, it would be 

 of great interest to test whether a change from second- 

 ary to primary aerobic processes is possible in parasitic 

 worms after they have been kept for a long time in 

 aerobic surroundings. In view of the encouraging prog- 

 ress that has been made lately with the problem of main- 

 taining parasitic helminths in vitro, promising results 

 may be expected. 



Finally, a word is necessary concerning the difficulty 

 of distinguishing, in some cases, between incomplete 

 oxidations in the presence of oxygen and incomplete ox- 

 idations induced by a lack of oxygen as described in the 

 preceding chapter. At high oxygen tensions — in the 

 range in which the oxygen consumption is independent 

 of the tension — no confusion is possible; the second phe- 

 nomenon does not occur, there being no lack of oxygen. 



