82 SURVEY OF TXVERTEBRATES 



worms (Well, 1931), or they may be so small and possess 

 a surface/volume ratio high enough to permit a relative- 

 ly large amount of oxygen to enter the body even at low 

 tensions. Von Brand (1938) explains on this basis Da- 

 vey's (1937, 1938) observation that small nematodes 

 from the sheep survive much better in vitro when oxy- 

 gen is present than when it is absent. Davey himself 

 postulated an aerobic existence also in the intestine. 



To sum up, then, we are of the opinion ( see von Brand, 

 1938) that the old controversy "aerobiosis or anaero- 

 biosis," with respect to intestinal worms, should be aban- 

 doned, and that it should be recognized that one animal 

 may, depending on its organization, live a predominantly 

 anaerobic life in the same surroundings in which another 

 worm is capable of leading a chiefly aerobic life. 



(b) Tissue helminths. The same variabil- 

 ity in metabolic relationships probably applies also to 

 helminths parasitizing tissues but this topic does not 

 seem to have been discussed anywhere in detail. The rea- 

 son is evidently that most of the facts tending to clarify 

 the issue have come to light only in comparatively recent 

 years. 



It can be stated with some degree of certainty that some 

 worms lead inside the host tissues a predominantly aero- 

 bic life. Stannard, McCoy and Latchford (1938) studied 

 the metabolism of Trichinella larvae. They found a well 

 developed aerobic metabolism though some anaerobic 

 processes persist even at high oxygen tensions. Under 

 anaerobic conditions the animals became more or less 

 motionless, but survived well. The cellular respiratory 

 system, as evidenced by the reactions to a variety of 

 respiratory poisons, suggests an aerobic rather than an 

 anaerobic existence. It should be remembered, however, 

 that the larvae are practically motionless once the host 

 tissues have formed the cyst wall around them. It is 

 possible that the procuring of oxygen might be difficult 



