Suitability of protuberances on the third eyelids of sheep as a biopsy site for lymphoid follicles.
Gross and histological morphologies of complete third eyelids from dead sheep were determined initially. Three distinct areas were identified for further detailed examination: the bulbar surface, smooth palpebral surface and the protuberances on the palpebral surface. PM samples were taken from 151 normal adult sheep. This indicated the maximum number of lymphoid follicles counted in a single tissue section of a protuberance was 36, making this surface the best sample site for further identification of pathological isoforms of the prion protein.