EFB'ECT OF RADIUM ON CELL DIVISION 209 



marked increase in the rate of oxidation taking place in the egg. 

 This increase is due to the increased activity of the oxidative 

 enzymes, such as nuclease. The continuance of the process of 

 mitosis depends on these enzymes, for if oxygen is withdrawn 

 cell division stops. Mathews has suggested that 



Autolytic enzymes also evidently become active, either because 

 they are set free from the nucleus, or because the nuclear materials 

 activate, directly or indirectly, the inactive enzymes of the cytoplasm. 

 . Since during cell division these enzymes are set free and 

 at the same time the chromatic elements are plainly losing substance, 

 it is possible that these two facts should be correlated and that the 

 conclusion drawn that in the resting condition of the nucleus enzymes 

 of various kinds stick to, or combine with, the nucleic acid and are 

 thus accumulated, made resistant, more stable and inert, and that dur- 

 ing caryokinesis and possibly at other time also, they are split off from 

 the acid, become free in the sap, enter the cytoplasm and rejuvenate 

 the cell by digesting its accumulated colloidal material. 



If it is granted that the phenomena of mitosis are dependent 

 on the activity of intracellular enzymes, then it is clear that if 

 these enzymes can be stimulated or retarded in their activity 

 the result will be an acceleration or a retardation in the rate of 

 cell division. I believe that the radiations of radium are able 

 to change the rate of enzyme action, and that this is at least a 

 partial explanation of the results recorded in these experiments. 



I have already reviewed briefly the hterature on the effect of 

 radium on enzyme action. There is some lack of agreement in 

 the results obtained by various observers. The radiations are 

 stated to retard the digestive action of pepsin and trypsin, to 

 accelerate it, and to have no effect whatever. Similar state- 

 ments have been made regarding other enzymes. Richards 

 ('14) has shown how these contrary results may be explained. 

 Using X rays on pepsin and diatase he found that a short 

 radiation has the effect of accelerating their activity, while a 

 longer radiation inhibits it. "Between these two strengths 

 lies a point at which radiation is non efl'ective." These results 

 on extracted enzymes are exactly similar to the results given in 

 this paper. A short radiation brought about a stimulation, 

 while a longer one produced a retard. Between these two limits 



