300 METABOLISM AND GROWTH IN SEEDS 



to day much more slowly than in the case of the controls. In addition, 

 many seeds seem to be permanently prevented from germinating, so 

 that at the end of a week the number which have commenced to grow 

 is far below that found in a lot of unradiated seeds. The seeds which 

 fail to germinate as the result of radiation are not killed, as is shown 

 by the undiminished CO2 production. Twenty-five radiated seeds 

 from the radiated lot described in the fourth experiment of Table II 

 which had failed to germinate after 7 days still produced CO2 at a 

 rate of 606 units per seed. 



These results indicate that no direct relation exists between the 

 effect of /3-rays on CO2 metabolism and growth in radish seeds. In 

 this respect they recall the observation of Warburg* and Loeb and 

 Wasteneys,^ that by decreasing the hydrogen ion concentration of 

 sea water, the O2 absorption of echinoderm eggs increases and at the 

 same time segmentation is prevented. 



Kimura* has shown that if living carcinoma and sarcoma cells 

 from the mouse are exposed in vitro to weak doses of x-rays the proc- 

 esses of oxidation which lead to CO2 production are stimulated and 

 that in the case of the sarcoma the growing power is increased to some 

 extent. Stronger radiation diminishes the CO2 production of both 

 types of cell and destroys their power of mitotic division and growth. 

 The important point which is demonstrated by the present experi- 

 ments, in contrast to those of Kimura, is that the changes in the rates 

 of CO2 production and cell division do not always go hand in hand; one 

 may be increased by exposures which retard the other. This conclusion 

 is not as unexpected as it may appear at first, for the pathological 

 changes which are produced in Hving matter by radiations, i.e. the 

 malformation of embryos, must be due to an unequal effect on various 

 processes which go on side by side. If all processes were affected alike 

 their courses might be run more rapidly or more slowly, but at any 

 instant the conditions of equiHbrium in the tissue would not be abnor- 

 mal. It is the specific action of radiations on certain physiological 

 processes in contrast to others which accounts for the characteristics 

 of their effects. 



* Warburg, O., Z. Physiol. Chem., 1910, Ixvi, 305. 



' Loeb, J., and Wasteneys, H., /. Biol. Chem., 1913, xiv, 355. 



* Kimura, N., /. Cancer Res., 1919, iv, 95. 



