IRRADIATION OF LIVING PROTOPLASM 627 



Many writers stress the fact that the nucleus is more sensitive to 

 radiation than the cytoplasm (Reiss, 311, Vintemburger, 376, Zirkle, 397). 

 The extreme point of view, to the effect that only the nucleus is sensitive 

 to radiation (Zirkle, 398), can certainly not be held, for irradiation of 

 cytoplasm alone is effective (Reiss, 311, Vintemburger, 376, Tchahotine, 

 356, probably also Feichtinger, 97). There are indeed some who claim 

 that the cytoplasm is more sensitive than the nucleus (Wail and Frenkel, 

 380, lasswoine, 168, Jansson, 177, Rochlin-Gleichgewicht, 317). The 

 argument need not concern us further. Certain it is that the cytoplasm 

 alone may be profoundly affected by all types of radiation. 



As yet there is httle information regarding the effects of radiation — or 

 of anything else — on the physical and physicochemical properties of the 

 nucleus. We must, therefore, confine our discussion to the cytoplasm. 



Neither the metabohc effects nor the purely cytological will be 

 considered here, for these are discussed in other papers. The physical 

 and physicochemical properties of the cells for which methods of study 

 have been developed will be treated. These are (a) permeability to 

 water and dissolved substances, (6) viscosity, (c) electrical charges and 

 potentials, {d) reaction. In addition, the direct visible effects of radia- 

 tions on living protoplasm will be discussed; the morphological aspects 

 of degenerative changes must be accounted for before cytolysis is com- 

 pletely explained. The paper embraces the following types of radia- 

 tions and particulate agents conveniently classified with radiations: 

 visible light, ultra-violet rays, roentgen rays, alpha particles, beta and 

 gamma rays, cathode rays, but not heat waves, Hertzian waves, or cosmic 

 rays. Although infra-red radiation certainly has an effect on living 

 material (Hertel, 143, Vogt, 377, W. Hoffmann, 156, Nelson and Brooks, 

 244, etc.), the action on protoplasm has scarcely been examined. Our 

 primary interest is in the effect of radiations on plant and animal cells, 

 and tissues in mass are considered only when information concerning 

 protoplasm may be derived from them. The literature on inanimate 

 colloids is not included here. Our treatment is not exhaustive; we wish 

 chiefly to advance a point of view that is based on what knowledge there 

 is of the physical and colloidal properties of protoplasm, and, therefore, 

 seems somewhat more purposeful than the prevailing "quantitative" 

 point of view. 



Many of the papers we have read have offered so little to our discus- 

 sion that we do not refer to them in the text. Perhaps half of these we 

 have included in the bibliography with the idea that perhaps the reader 

 who cares to consult them may find more than we did. 



PERMEABILITY 



The cell physiologist has always been impressed with the importance 

 of knowing the permeability of the living cell, and the changes in per- 



