B. RAJEWSKY 



Curve (/) in Figure 4 also presents a further dose-independent range of 

 about 5-dav mean survival time between the two constancy ranges of the 

 3-5-day and 7-day effects. The meaning and more precise localization of 

 this new effect has not yet been clearly recognized. Anatomically considered, 

 however, the effect is not connected with irradiation of the adrenal, or 

 the pituitary gland region. Further investigations on this point are in 

 progress. 



' Slit irradiation ' was attempted to locate more exactly the critical organs. 

 With these irradiations the whole animal's body is shielded by lead with 

 the exception of a 5-mm wide slit. In this way only the part of the body 

 actually placed under the slit was irradiated. The slit was brought above 

 different regions of the animal's body in a series of irradiations. The results 

 of these experiments are summarized in the diagram B in Figure 4. It can 

 be seen that the irradiation of only a narrow strip of the animal's body is 

 able to produce both the 3 • 5-day and the 7-day effects. The 3-5-day effect 

 can be obtained by irradiating only the region of the abdominal organs 

 mentioned above, especially by irradiating a zone containing the adrenal 

 and the kidney, while the 7-day effect can be obtained by irradiating the 

 region of the pituitary gland. Slit irradiation of other parts of the body 

 decreased the mean survival time, although to a very much smaller degree 

 than irradiation of the critical regions just mentioned. These results 

 indicate that the two dose independent survival times were essentially due 

 to local injuries and the next step was to determine the relative importance 

 of the different organs located in the sensitive regions. 



The following experiments were carried out with this end in view : 



(i) Animals were irradiated, which were splenectomized, adrenalecto- 

 mized or hypophysectomized before irradiation. 



{2) Individual organs of the animals were irradiated in situ : adrenal, 

 kidney, liver, spleen, intestine, and pituitary gland. 



(3) Different combinations of these organs were irradiated in situ. 



(4) An attempt was made to influence the reactions by the administration 

 of certain substances. 



Details of these experiments will be given elsewhere^ and the most 

 important results only will be summarized. 



Adrenal — White rats were exposed to radiation over the whole dose- 

 independent range from 800 to 1 5,000 r, but no constant survival time 

 was observed in adrenalectomized animals, and a significant dependency 

 of survival time on the applied dose {i.e. a rapid fall of the medium 



survival time with increasing doses ; curve -| \- in Figure 5) was 



found. Irradiation of the adrenal in situ, while all other parts of the 

 animal's body were shielded with lead, did not produce a direct effect ; 

 during the time of observation which lasted for 6 weeks, the animals stayed 

 alive. In another series of irradiations the adrenalectomized animals were 

 treated with 5 mg of cortisone twice daily after irradiation. These cortisone- 

 treated animals showed again the full dose-independent range of the 3-5-day 

 effect. It is, however, remarkable that the dose range over which the 

 3-5-day efTect occurs was not extended by treatment with cortisone — after 

 further increase of the dose up to approximately 1 5,000 r a rapid fall of the 

 animals' mean survival time occurred according to the general injury curve. 



87 



