248 RECOVERY FROM ANAEROBJO^SIS 



present state of our knowledge, however, we can only re- 

 view the few recorded disconnected investigations. 



So far only worms and insects have been studied. Dau- 

 send (1931) investigated the glycogen content of Tuhifex, 

 first in normal conditions, then after a stay of 22.7 

 hours in the absence of oxygen and finally in animals 

 that were brought back to aerobic conditions for 4 and 6 

 hours after having endured the 22.7-hour deprivation of 

 oxygen. He found a resynthesis of about 50 per cent of 

 the anaerobically lost glycogen, i.e., somewhat less than 

 in vertebrates. But his conclusions are based on only a 

 single series of experiments and, in view of the rather 

 pronounced variations in glycogen content in inverte- 

 brates, a re-investigation on a broader basis is very 

 desirable. 



Von Brand (1937) made a large number of experi- 

 ments with Ascaris and observed that 100 g. of worms 

 may rebuild 70 to 150 mg. of glycogen during recovery. 

 This corresponds to about 1/20 to 1/10 of the glycogen 

 consumed during the preceding anaerobic period. But 

 these figures might be somewhat low. During the recov- 

 ery period at the same time that some glycogen is re- 

 built, some of it may disappear as a result of the normal 

 metabolic processes ; the above figures show only the over- 

 all change. In any event, the resynthesis is much less 

 pronounced than in vertebrates, a fact connected with 

 the ability of these worms to excrete end products of the 

 anaerobic metabolism. It is clear that the eliminated 

 material is lost for resynthesis; only substances that 

 actually have accumulated within the tissues can be used. 

 Whether lactic or a lower fatty acid serves as substratum 

 for these processes in Ascaris is not yet known. 



In the case of Tenebrio larvae it has been proved defi- 

 nitely by Gilmour (1941) that lactic acid is resynthe- 

 sized to carbohydrate. He found in his animals, at the 

 beginning of the experiments, an average of 12.6 mg. 



