262 DJFFJ'JKENCJ'J.S IN ANAIJROB. FUNCTIONS 



received strong sui)port recently through Laser's (1944) 

 work on Ascarls. This worm is not a strict anaerobe, 

 but a euryanoxybiotic aero-fermenter which succumbs to 

 high oxygen tensions. Laser demonstrated, by a direct 

 chemical method, that in ascarids killed by oxygen an 

 accumulation of hydrogen peroxide occurs. The catalase 

 content of these worms is very low (Lesser, 1906) and 

 not sufficient to counteract the rapid hydrogen peroxide 

 production occurring at high oxygen tensions, but it 

 does suffice to destroy the amounts formed at low tensions, 

 Qr the peroxide may be eliminated in some secondary oxi- 

 dation reactions catalyzed by methaemoglobin. 



As to the third theory Jahn writes : ' ' The chief diffi- 

 culty in interpreting experiments pertaining to the effect 

 of Eh on growth is that it is necessary to change Oo ten- 

 sion in order to change En. This makes an experiment 

 containing only one variable seemingly impossible to exe- 

 cute, and the theory, therefore, has not been amenable to 

 experimental approach. ' ' 



On the fourth theory no experimental evidence has yet 

 been presented. 



Thus the available evidence is much too incomplete 

 to allow any conclusion on the mechanism of injury by 

 oxygen. A comparative investigation of the catalase 

 content and the susceptibility of invertebrates to oxygen 

 might be the most promising approach. 



2. W^HY CAN SOME INVERTEBRATES TOLERATE A LACK 

 OF OXYGEN WHILE OTHERS CANNOT? 



The ability to withstand the deprivation of oxygen 

 rests, presumably, on two conditions: {A) the organisms 

 should be able to gain sufficient energy from the anaerobic 

 metabolism and {B) they should be immune to the injury 

 usually occasioned by the accumulation of metabolic end 

 products. These two conditions will now be discussed. 



A. Ability to gain sufficient energy from anaerohic me- 

 tabolism. The only direct measurements of the energy 



