Seasonal changes in the inner root sheath of the primary follicles in Herdwick sheep

Abstract

The histology of the skin follicles of a small group of Herdwick ewes was examined in midwinter and again in midsummer. In the primary follicles which remained active (about 9 % of the total follicle population) the ‘winter thinning’ in the fibre was accompanied by a thickening of the Huxley layer in the inner root sheath. In heterotype fibres (from primary follicles) a poorly defined crimp and a bilaterally differentiated cortex were present only in the thin length of fibre grown in winter.The author is grateful to Dr. Marca Burns for permission to sample her Herdwick flock, and to Dr K. M. Rudall for helpful advice. This work was carried out while the author held a grant from the Agricultural Research Council.