GENERAL DISCUSSION 343 



muscle to cliemical factors is also altered in the direction of a decreased 

 sensitivity; simultaneously, the turning-point dose is also decreased — 

 it is moved from 50 to 35 kr. 



To transfer the ion displacements of one polarity into another will 

 require either a sufficient irradiation dose or the inclusion of additional 

 factors, in particular, an effect by i.r. rays following the X-rays, which 

 facilitates the effect of X-irradiation, and which is not shown after the 

 action of X-irradiation alone. 



In these experiments the thermal effect of the i.r. illumination is as 

 far as possible eradicated by sj^ecial filters and by the replacement of 

 the physiological solution. The i.r. radiation being applied as a sejiarate 

 factor does not cause any variation of the electrical properties of the 

 muscle. The action of the i.r. i*adiation 2 hr after the X-ray irradiation 

 halted the development of the displacements in the electrical properties 

 of the muscle, which are observed after X-ray irradiation, i.e. tended 

 to conserve the macromolecular complexes. These data are, in prin- 

 ciple, in agi'eement with those of Hollaender, although they were ob- 

 tained for different objects. According to our data, the i.r. irradiation 

 provokes for the most part that mechanism which determines the low 

 frequency electrical conductivity, i.e. affects the conditions for the ion 

 concentration at the polarized interphases. The degree of conservation 

 is connected with the original construction of the surfaces of the 

 membrane and is increased in the more complex structure of the skele- 

 tal muscle in comparison with smooth muscle. 



HUG : I would like to make several comments on the connection of the 

 problem of permeability with the action of radiation. 



Unfortunately, up to the present time there is only a small number 

 of direct proofs of the variation of the permeability in radiation con- 

 ditions. 



Only after irradiation with very high doses is a loss of potassium 

 ions observed. This, however, can be exj)lained by the fact that an 

 unsuitable method and objects were employed. Permeability should 

 be measured during the irradiation period and the kinetics of this 

 process must be studied. 



From the biophysical point of view one must expect here a strong 

 dependence upon the power of the dose and upon the linear energy 

 transfer. It is necessary to conduct new experiments and at the same 

 time to examine the old work from a new critical standpoint. 



Permeability is a far too general term. The difference in permea- 

 bility of the membranes for different substances is extremely large. 

 The permeation of inorganic substances must be distinguished from 



