The presence of acid mucopolysaccharides in the trabecular meshwork was repeatedly investigated histochemically. The electron microscopical demonstration of glycosaminoglycanes with Ruthenium red was to be emphasized. In the material gained by trabeculectomy in 13 patients, a Ruthenium-positive, up to 30 nm thick film of varying degree could be demonstrated on the endothelium of the trabecular meshwork.