XVIII 



THE ACTION OF RADIATIONS ON LIVING PROTOPLASM 



L. V. Heilbrunn and Daniel Mazia 



Department of Zoology, University of Pennsylvania, Philadelphia 



Introduction. Permeability: Visible light — Ultra-violet rays — Radium — Roentgen 

 rays. Surface charge. Protoplasmic colloids: Visible light — Ultra-violet rays — Roentgen 

 rays and radium. Conclusion. References. 



INTRODUCTION 



It is recognized that radiation affects protoplasm and protoplasts, 

 but whether or not this direct action may explain the effects of radiation 

 on organisms is another problem. Generalizations by radiologists have 

 appealed to protoplasmic effects out of all proportion to exact information 

 concerning these. The interest in an evaluation of our information, 

 therefore, extends beyond that of cellular physiology, which in itself 

 must be great. 



Our knowledge is admittedly slight. The number of radiation 

 experiments which consider direct protoplasmic effects even to the extent 

 of examining the cells microscopically is small. The observations to be 

 discussed in this paper were necessarily culled from outside the litera- 

 ture of cellular physiology, from plant and animal physiology, cytology, 

 pathology, bacteriology, and from clinical and experimental medicine. 

 The task is to impose upon these data the point of view and the criteria 

 of the student of protoplasm. 



The change of stress from the purely radiological to the physiological 

 implies in this case a new emphasis upon the qualitative. Quantitative 

 experiments in the literature of radiation are characterized by the use 

 of some conspicuous biological criterion, with reference to which the 

 results of changing the physical variables such as intensity, frequency, 

 and time are compared. The criteria typically used are death, change 

 in growth rate, change in division rate, abnormal fertilization, abnormal 

 development, etc., all complex phenomena whose components alone 

 have physiological meaning. 



It is premature to consider with great exactness the relations of the 

 physical variables in terms of diffuse and unanalyzed "biological" 

 effects. The first question is, what do the rays do to protoplasm — to 

 the cell? The mathematical treatment of exact mortality curves, for 

 example, is not a primary concern for us. The theories advanced in 

 terms of the physics of the radiation — especially the effects of radiations 



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