CHAPTER 1 



PHYSIOLOGICAL CHANGES PRODUCED BY X RAYS 



Virchow has stated that cellular reactions to 

 various irritants depend on the power of the 

 irritating agent. At first normal cellular activ- 

 ity is accelerated; exposures of longer duration 

 to stronger doses produce depression; prolonged 

 exposures result in death. This thesis has found 

 confirmation in the works of the most recent 

 investigators and was most precisely formulated 

 by Arndt*: "Weak irritants stimulate activity; 

 medium irritants depress it; strong ones halt 

 it. " This formulation has been extended by 

 Schultze to include all the vital processes of 

 animal and plant cells of diseased as well as 

 of healthy organisms. This generalization has 

 become accepted in literature as a basic bio- 

 logical law. 



Since X rays have a stimulating effect on the 

 activity of organisms, it was necessary to deter- 

 mine to what extent they conform to the Arndt - 

 Schultze Law. Few investigators objected to 

 that part of the law which states that strong 

 doses of radiation tend to suppress normal ac- 

 tivity. Numerous experiments testify to the 

 inhibition of development of organisms or tissues 

 that have been subjected to strong or prolonged 

 doses of radiation. Concerning the other part 

 of the law, however, opinion is sharply divided. 

 While some point out the stimulating effect of 

 weak doses, others deny this effect altogether, 

 or they acknowledge it only as a temporary 

 spurt of activity followed by normal, or even 

 depressed, development. For example, in 1923 

 Holtzknecht wrote: "We have no basis for 

 assuming that because a substance is harmful 

 that, in some amount or other, it may be bene- 

 ficial. Consequently, since X rays fatigue and 

 kill cells, we cannot conclude that doses exist 

 which stimulate or accelerate cellular develop- 

 ment. Fifteen years of roentgenology have 

 established only the depressing effects of X rays 

 on cellular activity. " 



It should be noted that the term "stimulation" 

 is ambiguous since stimulation includes negative 

 as well as positive responses to stimuli. Un- 

 doubtedly, certain differences of opinion stem 

 directly from the use of this word. In order to 

 avoid this type of misunderstanding the term 

 "stimulation" will be used in its more generally 



accepted sense, i. e. 

 reaction. 



to indicate a positive 



A dose of X rays which stimulates the life 

 processes of plants is commonly referred to as 

 a "stimulating dose." From the numerous 

 investigations of various authors it is evident 

 that some of them have succeeded in establish- 

 ing stimulating dosages for the subjects of their 

 experiments, while others deny the existence of 

 such dosages. 



One of the earliest investigators of the bio- 

 logical effects of X rays was Schober, who in 

 1896 set out to study the nature of X rays pri- 

 marily to determine whether or not they were 

 identical with light rays. Schober selected 

 germinating oats as the most light sensitive 

 object he could find. Having germinated oat 

 seeds in darkness, he selected the most vigor- 

 ous specimens (1 to 2 cm high) and planted them, 

 five to a cup, in four small cups. He then 

 placed the cups in a darkened box and subjected 

 them to the action of X rays for 1 hour, with the 

 source of the rays 1 centimeter away from the 

 box. Careful observation of these plants did 

 not reveal in them any evidence of [heliotropic] 

 bending. When the box with the cups was placed 

 on the window sill and a diffused light was per- 

 mitted to enter through a narrow slit, it was 

 possible after 1 hour to observe a bending of 

 the sprouts in the direction of the light. After 

 2 and 4 hours this bending was even more pro- 

 nounced. On the basis of this experiment the 

 author concluded that X rays were not identical 

 with light rays. 



Atkinson (1897) conducted experiments to 

 determine the effect of prolonged irradiations 

 on plants. Having established by preliminary 

 experiments that radiations of 1 to 10 hours do 

 not produce any visible signs of injury in 

 Caladium leaves, Begonia flowers, and in vari- 

 ous seedlings, he set up an experiment with 

 prolonged irradiations (45 -hour exposures). 

 This experiment was conducted in darkness. 

 The irradiated plants behaved identically with 

 the controls that had been grown together with 

 them in a dark room. When placed in light 

 both groups exhibited pale green color with this 



