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SUMMARY Clobetasone butyrate, a new corticosteroid with a high topical activity, has been compared with prednisolone phosphate and a placebo in the treatment of inflammation following cataract extraction. These 2 steroids were more effective in relieving postoperative inflammation than placebo (P < 0 05), though no obvious clinical differences between the 2 compounds emerged from this investigation. However, a single-blind comparative study against betamethasone phosphate in patients suspected of having steroid-induced glaucoma showed that, while betamethasone phosphate significantly raised intraocular pressure, clobetasone butyrate had only a minimal effect, and this difference was statistically significant (P <0 02).

THE pzesent experiments were designed to investigate the mechanisms by which a known volume of protected bone marrow may modify the response of the haemopoietic tissues to ionizing radiations, with special reference to the possible cellular interrelationsbps between bone marrow, thymus and spleen.In a standard guinea-pig, on whch extensive quantitative marrow data were already available, two limbs were shielded whilst the remainder of the body was irradiated. The cellular responses of the shielded and irradiated bone marrow, blood, thymus and spleen were followed throughout the recovery period, and compared with the effects of whole body irradiation, as previously reported in detail for the same animal and dosage (Harris, 1956(Harris, , 1958(Harris, , 1959(Harris, , 1960Osmond, 1962) and supplemented by further observations. MATERIALS AND METHODSThe studies were performed on 77 male Dunklin-Hartley guinea-pigs, weighing approximately 400 g. at the time of irradiation. IrradiationEach animal was given 150 r. gamma irradiation from a therapeutic 6oCo unit at a rate of approximately 20 r./minute. This dose, when given to the entire animal, produces a marked cellular depletion of the marrow and lymphoid tissues together with a low mortality rate of 5-10 per cent (Ellinger, 1945;Harris, 1956Harris, ,1958Harris, , 1959Harris, ,1960Osmond, 1962). The irradiation procedure was standardized to secure as constant and uniform a dosage as possible. Under sodium pentobarbitone anaesthesia (3 mg. per IOO g. body weight) the animals were immobilized against a wooden base board with their limbs M y extended. The irradiation was then delivered in two doses of 75 r. through the dorsal and ventral aspects of the body respectively. All irradiations were performed at approximately the same time of day (5-8 p.m.). ShieldingIn one group of 49 animals both left limbs were given a high degree of protection by two specially shaped lead blocks, 10 cm. in thickness. The blocks completely covered the limbs, including the upper ends of the humerus and femur, but gave little or no additional shielding to the bones of the limb girdles. Initial trials with a radiographic check showed that it was possible to align the lead blocks consistently by palpation of the bones in the immobilized, anaesthetized animal. To reduce the penumbra effect to a minimum the blocks were placed on inclined wooden planes, immediately above the limbs, at angles that were calculated to bring the leading edges parallel with the most divergent rays from the 'j0Co source. The latter was aligned over the centre of the unshielded area of the body.

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