ciency will be discussed under paragraphs 192-213. Once more, it should be pointed out that there is no fundamental biophysical reason why the shape of the neutron curve should be of the form roughly described by the above equations, because the same observations pointed out for the x- and gamma-ray data under paragraph 93 would be expected to apply to the neutrons as well. How- ever, the form of the neutron relationship is curvilinear (convex upward) within a range of effect where a linear function applies to low-LET relationships. Since saturation phenomena with respect to the expression of the biological damage might not be expected under such conditions, the only way to interpret the neutron data is by assuming that the shape of the relationship does reflect some primary biophysical difference in the mode of action of low- and high-LET radiation, particularly at the low doses. 96. The effects of single acute exposures of low-LET radiation on animals other than the mouse are summarized in Figure IV, in comparison with all the mouse data. At inspection, no large differences may be traced from the small series reported in the literature. This is particularly true for the rat, whose data are well superimposable up to 500 rad with the mouse response. The response of the dog has only been examined at relatively low doses and the data are perhaps on the high side of the mouse data. The chinese hamster, on the contrary, has only been examined at doses in excess of 500 rad and the data are suggestive of a concave upward trend. Between the species tested, however, the variability of the response is apparently rather small. B. OT. THE EFFECT OF CONTINUOUS LIFE-TIME IRRADIATION The "duration-of-life" exposure condition has been used since the very beginning and is documented in the early papers of Henshaw [H1], Evans [E2], Lorenz et al. [L6] and Boche [B11]. It has widely been utilized in the ex- perimental series of Sacher and Grahn [S4] who have largely contributed to the interpretation of this type of data and is still in use at present [N6, NT]. In this case of internal irradiation from radionuclides of long half-life it is naturally the only possible irradiation condition. Exposure for the entire life represents a base-line condition of irradiation useful for comparison with other exposure types like the acute single-dose: in respect to this lat- ter it has the advantage of mimicking a pattern of exposure which is the most interesting in practice, since the continuous chronic rather than the short i