Cytoplasmic granules of the corneal stroma cell.

I n 1955, Jackson described the existence of circulating cytoplasmic granules of polysaccharide-protein composition in the fibrogenic cells of bone, tendon, and cornea of the fowl embryo which were growing in tissue culture. Long-lasting metachromasia developed in these granules when toluidine blue or thionine was added to the culture medium. It was not specifically stated in that paper that these granules were found in corneal cells. Other investigators have mentioned or depicted a granular cytoplasm in normal adult keratocytes stained by the Rio Hortega technique," but Jackson's observation passed virtually unnoticed in relation to the corneal stroma cell. Undoubtedly, the principal reason for this neglect is the apparent extreme difficulty in preserving the granules for study. Conventional fixatives are sometimes inade-