646 



BIOLOGICAL EFFECTS OF RADIATION 



Cernovodeanu and Henri (57, 58) studied irradiated bacteria, proto- 

 zoa, and leucocytes ultramicroscopically. They found a brilliant 

 granular appearance which they considered identical with that of albumin 

 coagulated with ultra-violet. The use of the ultramicroscope for the 

 colloidal study of protoplasm is rather unsatisfactory (cf. Heilbrunn, 

 136, pages 38 to 39), so that the results of Cernovodeanu and Henri are 

 not very convincing. Addoms (1) likewise employed the ultramicroscope 

 to examine the protoplasm of wheat seedlings following irradiation with 

 a mercury-vapor lamp. She also concluded that coagulation occurred. 



In the course of some embryological studies, Schleip (330), among 

 others, described effects on the protoplasm of Ascaris eggs which indicate 

 a sharp increase in viscosity following irradiation with X2800 A from a 

 magnesium arc. Ruppert irradiated centrifuged eggs and determined 

 the time necessary for the return of the granules which had been moved to 

 one side of the cell. The time necessary for this return is much longer 

 than the time required in the case of normal untreated eggs. Inasmuch 

 as the return is almost certainly due to Brownian movement, there is 

 rather clear evidence of an increase in viscosity. 



Gibbs (118) used a mercury-vapor arc (X3126 to 2378 A) on Spirogyra 

 cells and found that the rays caused first a liquefaction and then a 

 coagulation of the protoplasm. He used the centrifuge method, which is 

 apparently appUcable to these cells (Heilbrunn, 136, pages 47 to 48). 

 The results are clear-cut, although not expressed in quantitative units. 

 Table 4 taken from Gibbs shows the decrease in protoplasmic viscosity 

 caused by relatively short exposvires. 



Table 4. — Effect of Ultra-violet Light on Spirogyra Protoplasm 



(Gibbs, 118) 



Time of centri- 

 fuging, sec. 



45 

 60 



75 



Cells exposed to 



unscreened arc for 



30 min. 



Slight displacement 

 Marked displacement 

 in some cells 

 Marked displacement 



Cells exposed to 

 arc screened with 

 "Noviol O" glass 



Normal 

 Normal 



Very slight dis- 

 placement 



Cells not exposed 



Normal 

 Practically normal 



Very slight dis- 

 placement 



Results somewhat similar to those of Gibbs were obtained by Heil- 

 brunn and Young (138) for Arbacia eggs. In their experiments, how- 

 ever, they treated the cells first and then noted the viscosity at varying 

 times after exposure. The centrifuge method was used, and the eggs 

 in a thin layer were exposed to the radiation for 1 min. Two minutes 

 later, the protoplasmic viscosity was found to have dropped to about 

 two-thirds of its original value. Then, after 15 min., it rose to 3 or 4 



