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Abstract
We have exposed suspensions containing the infective agent of scrapie to doses of ultraviolet light (u.v.) up to 12 times greater than those used in the experiments reported by Alper et al. (1967). Suspensions were prepared and assayed by the methods described by those authors and by Alper, Haig & Clarke (1966). Two different suspensions were irradiated on 2 days separated by a week and were exposed to nearly monochromatic u.v. at 254 nm. from a 15 w ‘germicidal’ lamp. All of the samples were assayed in duplicate and about the same level of activity remained after similar doses in both experiments (Fig. 1). Ultraviolet absorption spectra taken on several preparations made at various times, were constant within fairly narrow limits. Transmittances of the total samples (thickness 2 mm.) irradiated were 0.93. Samples were stirred during irradiation.
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