A light microscopical study of healing incised dermal wounds in rats, with special reference to eosinophil leucocytes and to the collagenous fibres of the periwound areas.

Incised wounding of rat skin had a significant effect on the number of eosinophils both within the scar and in the adjacent areas. The numbers increased, after the inflammatory phase, to a peak between the 7th and 12th-14th days after wounding and remained elevated for the rest of the 30-day experimental period. In the areas contiguous to wounds, the dense bundles of collagenous fibres characteristic of normal dermis became progressively more dispersed from the 3rd to the 14th day, and then gradually re-aggregated into bundles. The fact that eosinophils, which are known to be collagenolytic, increase in numbers and change in morphology at the same time as newly formed scar collagen is remodelled and fibres around wounds are aggregated indicates a role for these cells in connective tissue metabolism. It is suggested that the dispersion of the collagenous fibres in the areas around wounds which occurs before the rise in eosinophil numbers could be related to the known increase in sulphated glycosaminoglycans around incised wounds.