the shape of the curve should be taken with some reservation, particularly since Later tests with more refined dosimetric methods (which in this particular instance left something to be desired) gave more nearly linear doseeffect relationships. 63. In the Greenhouse series [U5] the Gompertz plot of irradiated mice showed a displacement upwards and to the left of the control curves in both sexes. Life-span-shortening was reported to be due to premature onset of all diseases observed in normal aging mice. The onset of old-age diseases was advanced to essentially the same extent by any one dose, an exception being thymic lymphoma whose incidence was greatly increased in both sexes. There was no consistent relationship between frequency of neoplasia and dose, because the incidence of some tumours (thymic lymphoma, granulocytic leukaemia, tumours of the ovary) increased but that of others with increasing doses. (reticulum cell sarcoma, mammary sarcoma) decreased Thus, no overall clear-cut relationship could be estab- lished between life-span-shortening and tumour incidence. 6h. Some of the data from the Greenhouse experiment (male and female ani- mals receiving up to 267 rad) were reanalised by Walburg [W1] on the basis of the original pathology data and with appropriate corrections for competing probabilities of death [H2, H4]. A significant life-shortening effect was observed when all causes of death were considered together; but when only non- neoplastic deaths were taken into account there was no advancement in time of mortality due to these diseases. Walburg concluded therefore that evidence of life~shortening due to non-neoplastic causes was lacking, although these experiments are often cited as an example of non-specific life-shortening. 65. Working on six mouse strains irradiation with single doses of x razs around the LD with dose. 3 Grahn [Gh] reported a curvilinear type of relationship oeaperopriate eorrection for animals dying of leukaemia and ova- rian tumours he was able to eliminate much of the variability between strains and sexes and to reconduct the whole process culminating in life-shortening to a basic injury parameter (0.28 days of life lost/R or 19 per cent life lost for irradiation at the LD ) applying to all strains and sexes. On this 50/30 basic parameter other factors, specific for life-shortening due to leukaemia and ovarian tumours, would superimpose to give predictable amounts of effect at any dose and for any strain and sex. Jordan !Vi] are summarized in Table 2. Other data by Vogel, Frigerio and