264 PLACE OF ANAEROJi. /.\ M ETA HOLISM 



^en is responsible for the early asphyxiation of many in- 

 \'ertel)rates. It has been observed (Buck and Boche, 1938; 

 Kichards, 1941) that in insects kept under anoxic condi- 

 tions chromatin clumping occurs in the nuclei of various 

 tissues. Eichards considers this change not as the ac- 

 tual cause of death, but rather as a criterion of asphyxi- 

 ation. It is of significance that this clumping was ob- 

 served especially in the cells of the central nervous sj^s- 

 tem of Culex larvae. As to the mechanism of the clump- 

 ing, Richards (personal communication) thinks that a 

 lowering of the cellular pH may explain it, as is sug- 

 gested by an observation of Nassonov (1932a) on a sim- 

 ilar phenomenon. It is indeed possible that sufficient lac- 

 tic acid accumulates during asphyxiation to change the 

 reaction of the cell content. If this view is correct, the 

 inability of the nerve cells to eliminate or detoxicate the 

 end products of the anaerobic metabolism would be large- 

 ly responsible for the early death of insects kept in anoxic 

 surroundings. 



B. Ifnniunization against the injury caused hy the ac- 

 cumulation of metabolic end products. It is a well-known 

 fact that a vertebrate muscle loses its ability to contract 

 in the absence of oxygen or when the oxygen supply is 

 insulticient, as in fatigue, because of the accumulation of 

 non-oxidized substances, primarily lactic acid. A similar 

 toxicity of the end products of the anaerobic metabolism 

 can be observed in many invertebrates. The actual ac- 

 cumulation of lactic acid has been demonstrated repeat- 

 edly in animals that are not well adapted to life in an- 

 oxic environments, for example, the earthworm (Davis 

 and Slater, 1928a), echinoderms ( Boyland, 1928) cock- 

 roaches (Davis and Slater, 1926), and other insects (Gil- 

 mour, 1941). But no quantitative determination has yet 

 been made of the concentrations which bring about re- 

 versible paralysis or which injure the animals irrever- 

 sibly. 



