658 BIOLOGICAL EFFECTS OF RADIATION 



ultimate coagulation of the main mass of the protoplasm. Experimental 

 evidence in favor of this view is presented. 



/. There is reason for believing that the plasma membrane of the cell 

 is, in part at least, a calcium gel. Release of calcium would presumably 

 liquefy or weaken such a gel. Hence it is understandable that radiation 

 should break down the cell membrane. Moreover, in view of the fact 

 that calcium, more than any other ion, is responsible for the semiper- 

 meability of the membrane, it is readily conceivable that release of 

 calcium from the cortex of the cell or from the membrane might cause the 

 permeability increase noted above. 



g. The points brought out above are in accord with those observa- 

 tions which show that calcium is set free from plant and animal tissues 

 after irradiation with ultra-violet, radium, or roentgen ray. A similar 

 effect has been described for proteins and it may be interpreted in terms 

 of a known action of rays on the carboxyl bond of amino acids. 



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