Reaction of protoplasm to radium radiation

Summary

• 1. The protoplasm of slime moulds (myxomycetes) is highly resistant to radium radiation (beta and gamma rays).

• 2. When radiation is concentrated directly on a small bit of plasmodium, all spreading stops and streaming is reduced. There is a slight increase in viscosity which, however, must be regarded as the result of a reduction in physiological activity and therefore the indirect result of radiation (which is probably true of most experimentally induced changes in viscosity).

• 3. Twenty hours of continuous radiation from nine 12-milligram needles at a distance of 1 mm. is the maximum time of tolerance of the plasmodium.

• 4. When radium needles are scattered in a culture of slime mould, the protoplasm advances to within a short distance of the needles, halts there for several hours, then advances to and over the needles; retreats after several hours; again advances until in contact with the needles; and again retreats.

• 5. No delayed lethal effect during five sub-cultures could be observed.

• 6. Two effects of radiation on cultures as a whole could be observed, though both were slight. The protoplasm is finder grained in the immediate vicinity of the needles; and radiated cultures are slightly better in growth and general appearance than the average controls.