IRRADIATION OF LIVING PROTOPLASM 635 



0.51 mg. of bromide with a gamma-ray activity equivalent to 0.27 mg. 

 of element. The capsules of radioactive material were placed directly 

 on the coverslip over the preparation. The rays caused a considerable 

 decrease in the average stomatal gap (ratio of width to length). Irradia- 

 tion also caused a 2- to 20-fold increase in the percentage of cells plas- 

 molyzed by a given hypertonic sucrose solution in a given time, which is a 

 fairly direct indication of an increased permeability to water, 



Packard (281, 282) presents evidence, largely indirect and wholly 

 qualitative, for an increase in the permeability of protozoa by radium. 

 He used 13.4 mg. of element very near the culture. He compared the 

 permeability (determined by the neutral red-NH40H method) of con- 

 jugating and normal Paramecium with their relative radiosensibility. 

 Similarly, the relative permeabilities of Paramecium and Stylonychia were 

 compared with their sensibility to the rays. The more permeable animals 

 always proved the more susceptible to the lethal action of radium rays. 

 From this he concluded that permeability increase was a factor in radium 

 cytolysis. Since 0.12 mm. of lead obviated all these results, he attributed 

 them to the soft beta rays. The later paper gives more direct evidence; 

 the irradiated and nonirradiated cells were tested by the indicator 

 method. Here Packard was able to demonstrate that permeability of 

 Paramecium to NH4OH increased as the dose of beta rays increased. 



In 1925 Van Herwerden (146) used the "reversible gelation" which 

 rendered the nucleus and nucleolus of epithelial cells in tadpole tails 

 visible, as a criterion of the penetration of dilute acetic acid. She exposed 

 a preparation of 3.1 mg. of RaBr2 (activity unspecified) for an hour or 

 two, then surrounded the cells by 0.05 to 0.07 per cent acetic acid. The 

 gelation appeared immediately. In nonirradiated controls 20 to 30 min. 

 were required to bring about the same result. Van Herwerden found her 

 results were not significantly affected by the interposition of 2 mm. of 

 lead, contradicting the results just mentioned of Packard who, however, 

 probably used larger doses. The reasoning of Van Herwerden is some- 

 what unsatisfying; if, as is more than possible, the rays themselves cause 

 a partial gelation, this might be summated with the acid effect, and the 

 end point would be reached sooner without any membrane change. 



The earliest evidence that erythrocyte permeability might be 

 increased by the rays from radium is that of Henri and Meyer (141). 

 They exposed a suspension of erythrocytes to 0.1 gm. of radium bromide 

 for 8 to 9 hr., then determined colorimetrically the degree of hemolysis 

 by a graded series of hypotonic solutions. Their data show a decreased 

 osmotic resistance in the irradiated cells, indicating augmented perme- 

 ability to water. This experiment has been carried out in a quantitative 

 way by Mascherpa (254) who, however, used only radium emanation, 

 which he dissolved in the experimental solutions and therefore permitted 

 to act during hemolysis. Table 1 gives his results. 



