988 BIOLOGICAL EFFECTS OF RADIATION 



1915 as marking the end of the pioneer stage of investigations of the 

 biological effects of radium rays. 



The results published between 1901 and 1908 (26, page 69) have been 

 summarized as follows: 



1. Radium raj's have the power to modify the life processes of both plants and 

 animals. 



2. Roentgen and radium rays produce similar 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 

 either to retard or to 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. 



In Chap. II of this memoir, the then existing literature was reviewed 

 showing that radioactivity and free electrons are a part of the normal 

 environment of probably every plant. The new work reported included 

 a study of the effect of the rays of radium and of its radioactive emanation 

 on various physiological processes of plants, as follows: (a) germination 

 of seeds ; (6) growth ; (c) photosynthesis ; {d) conversion of sugar to starch 

 in plant tissues in darkness; (e) respiration (aerobic and anaerobic); 

 (/) alcoholic fermentation; {g) tropistic response; {h) nuclear division. 



In addition, studies were made of histological modifications produced 

 by exposing growing roots, stems, and leaves, including nuclear structure, 

 and also effects that followed the exposure of germ cells to the rays. 



It would appear that in this memoir there was reported for the first 

 time experimental evidence that the rays of radium may, under suitable 

 conditions of exposure, induce an acceleration of vital functions. Thus, 

 by inserting a sealed glass tube of radium bromide into soil at suitable 

 distances from newly planted seeds their germination and the subsequent 

 growth of the seedlings were markedly accelerated. Only retardation or 

 cessation of germination and growth, or the killing of the seeds, had 

 hitherto been reported. It was found that the processes of respiration 

 and alcoholic fermentation might be greatly accelerated. Previously, 

 Dixon and Wigham (in 1904) reported that exposure to the rays checked 

 the action of enzymes, and Micheels and de Heen (in 1905) observed that 

 the rays retarded respiration. Guilleminot, in 1907, referred to an 

 accelerating action, if such exists. 



The experimental results led to the broad generalization that radium 

 rays act not, for example, like a stroke of lightning or immersion in boiling 

 water, but as a true stimulus to metabolism. "If this stimulus ranges 



