Foci of melanization were occasionally seen to be associated with setal ducts and:or
tegmental glands and probably reflected the susceptibility of tegmental glands and setal cells to infection. Other melanized encapsulations in the epithelium may have been related to stimulation of inflammatory cells by a bacteraemia or toxic products (Johannson & So¨derhall 1989). Total loss of epithelium (ulcer formation) resulted in the most severe and penetrating inflammatory response, probably reflecting the critical importance of this tissue as a barrier to infection.