RECOVERY FROM ANAEROBIOSIS 237 



however, questionable whether this condition actually 

 occurs in any invertebrate capable of consuming oxy- 

 gen. Adam (1932) and Harnisch (1933a) had observed, 

 it is true, that the oxygen consumption of Ascaris was not 

 markedly increased after a period of experimental an- 

 aerobiosis, but Harnisch found that isolated anterior 

 parts of these worms contracted an oxygen debt, and 

 Laser (1944) showed that, after 18 hours of anaerobiosis, 

 the oxygen consumption of entire ascarids was definitely 

 above normal for a period of about 2 hours. The repay- 

 ment of the incurred oxygen debt is quite incomplete, due 

 to the fact that Ascaris is capable of excreting a large 

 percentage of the anaerobic end products. 



Other cases of incomplete repayment are also known. 

 A graph by Thomas (1942) representing the oxygen con- 

 sumption of Tetrahifmena under normal conditions and 

 after 45 minutes in the absence of oxygen shows that this 

 ciliate repays only about 25 per cent of its oxygen debt 

 (the author does not discuss that point). Another case 

 is that of the larva of Eustrongylides ignotus, studied 

 by von Brand (1942). In that animal the excess oxygen 

 consumption, after a 16 to 18-hour period of anaerobiosis, 

 corresponded to about 30 per cent of the oxygen deficit. 

 Both these organisms are known to excrete acids during 

 the anaerobic period proper. 



The case of Zootermopsis nevadensis is more difficult 

 to understand. Cook (1932) stated that this organism 

 does not show an increased oxygen consumption after 

 anaerobiosis, but this was not corroborated by Gilmour 

 (1940) who thinks that Cook's result must be explained 

 by his failure to control the movements of his animals 

 which were responsible for an abnormally high pre-an- 

 aerobic level of oxygen consumption. Gilmour found a 

 repayment of 50 per cent, both in termites harboring 

 their normal intestinal fauna and in defaunated ones. 

 This low value is somewhat surprising since insects in 



