The sensitivity to radiation depends on the 

 amount of water held by the living protoplasm. 

 The criterion that indicates the loss of water 

 from protoplasm is the growth of the cell. The 

 ability to grow is connected with a definite de- 

 gree of turgidity of the protoplasm and it consti- 

 tutes a very sensitive indicator of turgidity loss. 

 The loss of water in Erdmann's experiments 

 was produced by potassium chloride, sodium 

 chloride, or urea. These experiments showed 

 that when protoplasm lost its turgor, the effect 

 of X rays was reduced by 25 to 30% by compari- 

 son with cells whose protoplasm was in the 

 normal state of turgor. If yeast cells from a 

 hypertonic solution were transferred to tap 

 water, irradiation produced the same effect 

 on yeast cells as when loss of water had not 

 taken place. Desiccation lowers the sensitivity 

 of the cells to radiation as when water is 

 removed by hypertonic solutions. The sensi- 

 tivity of older cultures of yeast is reduced by 

 35% in comparison with normal ones. Actually, 

 the aging of yeast cells is also accompanied by 

 loss of water which accounts for the reduction 

 of sensitivity. 



Heilbrunn and Mazia [1936] forms a chapter 

 in Duggar's book. In this chapter, the authors 

 discuss the idea that even if there is no doubt 

 that irradiation affects the protoplasm and the 

 cells, we still cannot know whether this is the 

 effect of the direct [primary] action of radiation 

 on the organism because our knowledge in this 

 area is still very limited. Even where cells 

 are examined microscopically, the number of 

 experiments devoted to the study of the direct 

 [primary] effects of radiation on protoplasm is 

 insignificant. The authors consider that our 

 primary interest should be in primary action of 

 irradiation on living protoplasm and in the study 

 of this action by means of physico-chemical 

 methods, namely, 1) permeability to water and 

 dissolved substances, 2) viscosity, 3) electrical 

 charges and potentials, and 4) chemical reac- 

 tions. 



Permeability, or rather, changes in perme- 

 ability due to the action of visible and ultraviolet 

 light and radium [radiation] were studied in both 

 animal and plant cells; while the investigation 

 of the effects of X rays was performed, chiefly, 

 on animals. Brummer^has shown that on human 

 skin2and on erythrocytes irradiation diminishes 

 permeability, whereas Hassel [Gassul]^and 

 Hoffmann^ indicate that permeability increases. 

 The data of Kroetz-*^ and Kov^cs^are equally 

 contradictory. Comparing the speed of chloride 

 diffusion through the normal frog skin and 

 through skin which had been exposed to 10 to 



* References not given but can be found in the ref- 

 erences cited in Heilbrunn and Mazia [1936] . 



^Editorial comment: Brummer found that irradia- 

 tion increases permeability in human skin. 



30 HED, the former demonstrated an increase 

 in permeability [of the irradiated skin] of almost 

 200%. Kov^cs, on the other hand, was unable 

 to establish any difference [of permeability] due 

 to X irradiation. Finally, Seckt (1902), while 

 observing changes in the stomata openings after 

 irradiation, established an increase in perme- 

 ability due to irradiation on a single plant 

 organism ( Tradescantia selloi). 



Viscosity . An investigation of changes in 

 viscosity of the protoplasm due to the action of 

 radiation of different wave lengths, ranging 

 from the ultraviolet to X rays and radium 

 [radiation], showed Heilbrunn [and Mazia] that 

 the main mass of the protoplasm (Plasmosol) 

 first became liquid and then, as the dosage was 

 increased, more viscous. While the internal 

 protoplasm became more viscous, the external 

 layer became diluted to 1/4 of its original state. 



Changes in cytoplasm, after irradiation are 

 similar in the tissues of various organisms, 

 although the difference in the degree of radio- 

 sensitivity of tissues, in general, is obvious. 

 Temporary stimulation of the physiological 

 processes is the first stage of the effects of 

 X rays. This is followed by gradual diminution 

 of activity and finally by complete inactivity. 

 A great many observations were performed on 

 protoplasmic movements (Lopriore [1897], 

 Nadson [and] Rokhlina [1926, 1934], Williams 

 [1923]) on motility of chondriosomes, fat glob- 

 ules, etc. , which indicate corresponding 

 changes in viscosity as well as the selective 

 permeability of protoplasm (Nadson [and Rokh- 

 lina, 1926 and 1934]). Protoplasmic strands 

 are drawn into the permanent cytoplasm and 

 accumulate around the nucleus or in some other 

 place; their cytoplasm gradually becomes turgid 

 as a result of formation of granular, small fat 

 globules, whose number and size gradually in- 

 crease, and finally, first small and then large 

 vacuoles appear (Nadson and Rokhlina [1926, 

 1934], Heilbrunn [and Mazia, 1936], et al). 

 When these changes become irreversible, death 

 occurs (Lopriore [1897], Nadson [and Rokhlina, 

 1926 and 1934]). The vacuoles may increase in 

 size or the protoplasm may disintegrate. 



Irradiation induces changes that are similar 

 to Dauer modifications, which is particularly 

 clearly demonstrated in Drosophila . These are 

 cytoplasmic changes that in subsequent genera- 

 tions revert to the original state. Many of 

 these changes, for various characters, were 

 described by Stein (1922 to the present [1946*]) 

 in irradiated snapdragons. 



Certain investigators have also noted that 

 even where reversible changes were effected, 

 the reversibility was often partial and that 

 cytologically imperceptible changes may be 

 retained and [later] manifest themselves by 

 formation of new tissues and possess, in the 

 final analysis, cytogenetic significance. 



62 



