1000 BIOLOGICAL EFFECTS OF RADIATION 



response as any activity or modification of activity tending to restore 

 perfect adjustment of the organism to its environment, we see that when 

 the radium rays are first introduced (stimulus), the retardation of growth 

 (response), under suitable conditions of strength and duration of stimulus, 

 is followed by a condition of tonus, the sporangiophore becoming adjusted 

 to its new environment which includes the radium rays, and growth 

 becomes steady again. Then, when the radium is removed, another 

 stimulus is thereby produced to which the sporangiophore again makes 

 response. Blaauw and Heyningen note that the initial influence of the 

 light rays and the gamma rays is of quite a different nature, touching a 

 quite different "link of the process of metabolism." 



In studying the action of radium rays on plant cells Maud Williams 

 (87) used strips of tissue from the upper surface of the petioles of Saxifraga 

 umbrosa and, for comparison, the movement of the chloroplasts in the 

 leaf cells of Elodea. After a short exposure there is an increase in the 

 rate of protoplasmic circulation. The cells were rendered permeable 

 and slow exosmosis of solutes can occur before any visible changes are 

 found in the protoplasm. "Large dosage" produced shrinkage of the 

 protoplast and vacuolation effects. Aftereffects "of more profound 

 nature" than the immediate effects are reported. For example, if the 

 radiation ceased before any shrinkage of protoplasm had taken place, and 

 the material was then placed in fresh tap water and kept in darkness for 

 24 hr. or longer, great differences between these cells and those of the 

 control material became visible. The protoplasm, often very discolored, 

 either collected in a dense mass in the middle of the cell or became very 

 dense at one end and very vacuolated at the other. The chloroplasts 

 did not lose their color or appearance. The length of exposure needed 

 to produce this after-appearance, depended upon whether Saxifraga or 

 Elodea was used, and also upon the season of the year when the tests 

 were made, Any change is irreversible after it has once become 

 visible. 



The modification of the physiological action of radium rays by the 

 presence of various chemicals has been investigated by several authors. 

 Rouppert and Jedrzejowski (68) exposed pieces of leaves of Ficus 

 Ficadatsura having their lower surface covered with unicellular emergen- 

 cies, and likewise young sprouts of Leea coccinea for 18 hr. to alpha, 

 beta, and gamma rays of radium and of the "active deposit" of strengths 

 15 and 3 millicuries, respectively. With 15 millicuries the pieces of leaves 

 and their unicellular emergencies of Piper were killed, but the multi- 

 cellular emergencies of Leea remained alive. In the second case (3 milli- 

 curies), all the emergencies remained alive whether the subjacent tissues 

 were killed or not. Even when the emergencies were nearer to a radium 

 tube than the body of loaf tissue, they remained turgid and uninjured. 

 The authors believe that the resistance of the emergencies is due to the 



