Fig. 15. A red blood cell (RBC) is seen passing through a pore in the flat portion of the endothelium (En) to the lumen of Schlemm's canal. The endothelium extends a funnel-like process toward the meshwork side. ER, endoplasmic reticulum; Th, thorotrast (12,000×). (From Inomata H, Bill A, Smelser GK: Aqueous humor pathways through the trabecular meshwork and into Schlemm's canal in the cynomolgus monkey (Macaca irus). An electron microscopic study. Am J Ophthalmol 73:760, 1972, with permission.)