THE MITOTIC CYCLE 



begin division only when a comparatively high level of energy is 

 available, such as that supplied by aerobic glycolysis. Medawar^"^ 

 has found that adult rabbit skin survives in cultivation in the absence of 

 oxygen, but that no cells then enter division. 





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Figure 66 The mitotic index in chick tissue cuhures treated 

 with gas mixtures containing carbon monoxide. No immediate 

 effects on growth are detectable. From Pomerat and 



VViLLMER^^* {By courtesy, J. exp. Biol.). 



The literature on the effects of anaerobiosis on cell division is re- 

 viewed by Braghet.210 Steinitz^" found that when barley seedhngs 

 were placed in an atmosphere of nitrogen, mitosis continued for 

 several days, although abnormalities of the chromosomes were then to 

 be seen. Mitosis in the sea-urchin egg can be inhibited at several stages 

 in an atmosphere of hydrogen (Harvey^^^) ; but it has not been proved 



