The occurrence and relationship of various complaints in lambs and hoggets, preventable by selenium prophylaxis, are reviewed. The excretion and tissue retention of selenium by animals on normal feeds and on oral dosing with sodium selenite are given. Faecal excretion of selenium, even on low levels of intake, is high and it is suggested that reduction of dietary selenium to a non-available form occurs in the rumen. In all animals investigated, the kidney showed the highest selenium levels and was the organ most influenced by selenium absorption. The kidney selenium levels provide an adequate index of the animal's selenium status. Tissue selenium levels from healthy, white muscle, and ill-thrifty lambs and hoggets were investigated. There is evidence that the occurrence of muscular dystrophy in lambs, but not necessarily in hoggets, is related to lowered tissue levels of selenium. Findings with respect to ill-thrift and selenium tissue levels were equivocal. The above work is considered together with published information on the nutritional causes of muscular dystrophy in sheep.

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Summary. Histological changes aud tbe accretion of calcium ami phrwphonis in au expi'iinicnhilly induced calcification of rat skin ("topical calcipliylaxis") have been described. Tbe appearance of mineral deposits was rapid and mild injury (epilatiou or light .squeezing) was sufficient stimulus tt> eause a sparse, restrieted mineralisation wbicb, with prior treatment of the animal witb an hyperealeaemie agent, progressed to give a grossly mineralised skin area. The initial mineralisation wa.s restricted to the hair follicle, and the deposition of hydrnxyapatite crystallites witbiu cells of tlie inner ront shcLith of the folliele and witliiu the corlev of the hair was demonstrated by clectrou microscopy. Tbis preferential mineralisation of the folliclo was not assnciitt'd with obviou.s degenerati\'e ebangcs anti tlic folliele remaineti functional. Tbe low-level calcification wa.s not species restricted and could also be demonstrated in rachitic rats in which u full "ealeipbylactic" response could not be elicited.Tbe implications of keratin mineralisation are diseu.ssed, and tbe findings of this study are considered in relation to eurrent concepts on the ealeifieation mechanism.