for partial irradiations of various types, an explanation that fails to account for the life-shortening at doses far lower than those responsible for the modes of death mentioned above. 321. In other experiments young female Wistar rats were irradiated on the whole body or on sections of it (head, upper abdomen, whole body except the upper abdomen) with a single exposure of 1000 R of 250 kVp x rays under anaes~ thesia and therefore under slight anoxia. Mean and median survival times of the groups receiving partial— or whole-body exposure were all reduced compared to controls. Life-shortening observed after partial-body irradiation was in approximate proportion to the weight of the irradiated tissues. Nephrosclero- sis was not seen unless the upper abdomen were included in the irradiation field and, except for the kidney, the spectrum of diseases observed at death in control, partial-body or whole-body irradiated animals was very similar. Inflam- matory diseases of the thoracic organs and benign and malignant neoplasms pre- dominated [L171]. 322. The results of Taketa [T2] were also obtained in the rat (adult male Sprague-Dawley, 9-11 weeks old) and involved exposure of the intact abdomen exlcusive of the gastrointestinal tract shielded) to 1300, 3500 or 5000 rad. (which was surgically exteriorized and A dose of 1300 rad to the intact abdomen resulted in 100 per cent of the animals dying within 4 days of exposure. The same dose given to the abdomen without the intestine allowed survival of the animals to a mean life-span of 262 days. But an increase of the dose to 3500 or 5000 rad under the same conditions shortened the life-span of the rats to 82 or 33 days, respectively. Results with the lower or the upper abdomen ir- radiated separately (with exteriorized and shielded intestine) were less clear. 323. Carsten and Innes [C26] working on female rats of the CFN strain irra- diated with 250 kVp x rays showed that 650 rad given to the lower body or 1300 rad administered to the upper body had a life-shortening effect of about 90 days (against a control value of about 700 days). The effect was statistically dif- ferent from the control life-span, but was very similar for the two treatments. Mammary adenofibromas developed in 60 per cent of the normal aging mice. Aecce- leration of these tumours was induced by irradiation of the lower, but not of the upper, body. These tumours were a major cause of death in both the irra- diated and the non-irradiated rats.