RECOVERY FROM ANAEROBJO^IS 241 



probable reasons for the very high post-anaerobic oxygen 

 consumption of the organisms mentioned in this para- 

 graph will be discussed in a later section. 



Besides the papers reviewed so far, which give quan- 

 titative data on the repayment of an oxygen debt, there 

 are several others which only discuss the problem in a 

 more general way, in particular those of Lund (1921), 

 Dahr (1927), Jatzenko (1928), Kreps (1929), Hiestand 

 (1931), van Dam (1935), Harnisch (1935a, 1935b, 1936, 

 1937b, 1939, 1941) and Gompel (1938). One more re- 

 mark remains to be made here. The time required for the 

 removal of the accumulated end products is occasionally 

 much longer than in the examples used for illustrating 

 the repayment of an oxygen debt. This happens, as has 

 been shown especially by Gaarder (1918) for the Tene- 

 hrio pupa and by Jatzenko (1928) for lamellibranchs, 

 when the anoxic period is long and the animals do not 

 excrete large amounts of the end products. 



We now turn to the question whether the post-anaero- 

 bic excess oxygen consumption shows characters differ- 

 entiating it from normal respiration. According to Har- 

 nisch the post-anaerobic reaction is much more dependent 

 on the oxygen tension, as observed in many different an- 

 imals, especially in Tuhifcx (Harnisch, 1935a, 1935b, 

 1936), Plmmria (1935b), Chironomus larvae (1936, 

 1937c) and Ephemera larvae (1939). Some of his curves 

 are presented in Figure 9. 



Harnisch (1935b) suggests two possible explanations 

 of this phenomenon: (1) That the preceding anaerobiosis 

 lias brought about a fundamental change in the ''internal 

 milieu" and, consequently, in the normal course of aero- 

 bic energy production; (2) That the animals make use 

 of two types of aerobic processes : the first, which would 

 take place during normal respiration (primary aerobio- 

 sis), would be largely independent of the oxygen tension 

 prevailing in the medium; the second would come into 



