650 BIOLOGICAL EFFECTS OF RADIATION 



interior may be transitory, so that one is likely to overlook it unless 

 viscosity determinations are made immediately after the rays begin to 

 have effect. In the cortex of Amoeba, the rays cause a liquefaction which 

 persists. This liquefaction of the cortex probably also involves a 

 weakening of the very outer surface of the cell; hence the frequent 

 descriptions, in the literature, of cell-membrane rupture following 

 irradiation. The liquefaction of the cortex is apparently due to a release 

 of calcium. In view of the fact that calcium is apparently the ion most 

 important in preserving the semipermeability of cell membranes (cf. 

 Lucke and McCutcheon, 244) and may very well enter into the substance 

 of the plasma membrane, it is easy to understand why ultra-violet radia- 

 tion (and indeed radiation in general) should increase the permeability 

 of the cell. 



If calcium is released from the cortex — and there are various indica- 

 tions in favor of this view — it would diffuse into the cell interior and 

 cause first liquefaction, and then if enough of it were present, coagulation. 

 Excess of free calcium in the cell interior causes the vacuolization reaction 

 so common in all types of protoplasm (Heilbrunn, 136). This vacuoliza- 

 tion reaction, as noted above, may be compared to the clotting of blood. 



Thus we have a mechanism of extreme delicacy, one that can account 

 for the radical colloidal changes observed, without recourse either to the 

 insensitive process of ordinary coagulation or to a purely hypothetical 

 mechanism such as special enzyme effects or point-heat effects. This 

 reaction accounts for (though it does not explain) the morphological 

 concomitants of radiation effects, and for the fact that the stimulating 

 and injurious effects of rays in protoplasm are essentially the same as the 

 effects of other effective physical and chemical agents. Presumably 

 the protoplasmic clotting, like the blood clotting, involves complicated 

 phenomena, and apparently thrombin-like substances are produced. 

 Just as when blood clots, it produces substances which affect unaltered 

 blood, so when the protoplasm of one cell clots, it may give off substances 

 which affect neighboring cells. It is thus possible to interpret the 

 necrohormone hypothesis which is popular with many radiologists 

 (Caspari, 55). 



ROENTGEN RAYS AND RADIUM 



As far as present-day information goes, the effects of roentgen rays 

 and of radium radiation on the colloids of the cell are in all respects 

 essentially the same as those described for ultra-violet. Exactly the 

 same cycle of viscosity change appears, and the coagulated protoplasm 

 presents the same morphological appearance. Beyond much doubt the 

 fundamental mechanism is identical. Indeed the more one studies the 

 colloid chemistry of protoplasm, the more apparent it becomes that 

 the protoplasmic colloid is so constituted as to be sensitive to various 



