290 



SCIENCE 



[N. S. Vol. XLII. No. 1079 



made. The controls gave rise largely to 

 active worms, but radiated eggs developed 

 only into irregular cell-masses or misshapen 

 little worms which were especially irregular 

 at the tail end, the results depending upon 

 whether stronger or weaker intensity of 

 radiation was used. He says that aU three 

 elements which normally take part in 

 mitosis were formed. Centrosomes, spindles 

 and fibers were alike all clear in the experi- 

 ment and in the controls. The chromosomes 

 divided irregularly, and in Ascaris megalo- 

 cephala univalens the characteristic num- 

 ber was doubled, knotty swellings appear- 

 ing on the chromatin loops instead of the 

 normal arrangement, and in some places 

 the chromosomes were broken up into nu- 

 merous unequal pieces. The injury to the 

 eggs expressed itself in the slowing down 

 of the development, which gives rise to ab- 

 normal individuals. The results with 

 X-rays were entirely analogous to those 

 with radium, delaying cell division and giv- 

 ing rise to abnormal products of develop- 

 ment. In both cases, the chief effects of 

 radiation on the cells appeared indirectly, 

 but only after the lapse of a certain period 

 of time. Eggs in the resting and in the 

 dividing condition served equally well for 

 the experiments. 



Sehaper exposed frog eggs as well as 

 Triton embryos to radium for varying 

 lengths of time. He observed an inhibitory 

 effect on cell division, on embryonic differ- 

 entiation, and on growth. There was also 

 an inhibition of regeneration which was 

 recognized after a longer or shorter period. 

 The latent period usually lasted almost a 

 day, the duration depending on the inten- 

 sity of the radiation and on the stage of 

 development of the organism. The period 

 of development was always more or less re- 

 tarded and prolonged. Finally it reached 

 a standstill and then death resulted. He 

 thinks there is some relation between the 



manner of solution of the yolk and the 

 effect of the radiation. In older larvse, the 

 living substances were used up and acute 

 degenerative changes in the cells set in. 



Gager' reviews the literature on this sub- 

 ject up to 1908 and summarizes the state of 

 knowledge at that time in his last para- 

 graph as follows: 



The broadest, and at the same time the most 

 definite generalization warranted by the work so 

 far done is that the rays of radium aet as a stim- 

 ulus to metabolism. If this stimulus ranges be- 

 tween minimum and optimum points, all metabolic 

 activities, whether constructive or destructive, are 

 accelerated, but if the stimulus increases from the 

 optimum toward the maximum point it becomes 

 an over-stimulus, and all metabolic activities are 

 depressed and finally completely inhibited. Be- 

 yond a certain point of over-stimulus recovery is 

 impossible, and death results. 



His review of the previous investigations 

 he brings together in the following state- 

 ments : 



1. Eadium rays have the power to modify the 

 life processes of both plants and animals. 



2. Eontgen rays and radium rays produce simi- 

 lar physiological results. 



3. Sensitiveness to these rays varies with the 

 species of either plant or animal. 



4. Younger, and especially embryonic tissues, 

 are more sensitive than those more mature. 



5. With only one or two exceptions, exposure to 

 radium rays has been found to either retard or 

 completely inhibit all cell-activities. The rays may 

 cause irregularities in mitosis. 



6. Experimental evidence for or against the 

 existence of a radiotropic response is conflicting. 



7. Whatever the immediate, internal change 

 produced in the protoplast may be, the result, with 

 animals as well as with plants, appears to be more 

 or less profoundly modified by the presence of 

 chlorophyll in the cell. 



8. Radium rays appear to retard the activity of 

 enzymes. 



Since the publication of Gager's results 

 on the effect of radium on plants a large 

 amount of work has been done in the labo- 



^ Loc. dt. 



