60 PROTOPLASM OF ^ROTOZOA 



THE EFFECTS OF RADIATION 



The Specific effects of radiation upon the cell are unknown. Further- 

 more, whether the nucleus or the cytoplasm is more susceptible to radia- 

 tion is a debated question. According to Heilbrunn and Mazia (1936), 

 Glocker and Reuss claim that isolated cells are less sensitive to Roentgen 

 rays than are cells in mass. 



The permeability of 'Paramecium and Stylojiychia to NH^OH has been 

 shown to increase with increased exposure of the animals to radiation 

 (Packard, 1923, 1924). After reviewing the literature on the biological 

 effects of radiation, including numerous studies on Protozoa, Heilbrunn 

 and Mazia (1936) reach the conclusion that ultra-violet rays, Roentgen 

 rays, and radium all cause liquefaction of the protoplasm and, with an 

 increase in exposure, coagulation. Coagulation of the protoplasm is fre- 

 quently preceded by extensive vacuolization. Furthermore, Heilbrunn 

 and Daugherty (1933), from their work on the effects of ultra-violet 

 rays on Amoeba, offer the theory that the effect of radiation is to release 

 the bound calcium from the cell cortex; it then enters the endoplasm, 

 causing first liquefaction and then gelation. Likewise, ultra-violet radia- 

 tion causes a release of fat in Amoeba (Heilbrunn and Daugherty, 

 1938). For the recent ingenius method of "microdissection" with ultra- 

 violet rays, see Tchakhotine (1937). 



THE EFFECT OF HEAVY WATER 



E. N. Harvey (1934) has studied the effects of heavy water on Para- 

 mecium, Amoeba, Euglena, and Epistylis (see also Taylor, Swingle, 

 Eyring, and Frost, 1933). Harvey found that paramecia were killed by 

 80 to 100-percent heavy water in from 6 to 10 hours. They first swim 

 slowly, appearing bloated; the contractile vacuole stops functioning; blis- 

 ters appear, followed by disintegration. However, they were not markedly 

 affected by 0.2-percent heavy water. Amoeba rounds up and is killed in 

 from 4 to 6 hours in 80 to 100-percent heavy water. Euglena, on the 

 other hand, is not irreversibly injured by 90 to 97-percent heavy water. 

 Gaw (1936b) found Blepharisma to become more spherical in 95-per- 

 cent heavy water, which indicates a change (decrease in viscosity) in the 

 physical nature of its cytoplasm. 



