Fig. 19. Evidence of tight junctional complexes in the anterior ciliary epithelium of Macaca mulatta. The pigmented epithelial cells (PC) are outlined by a thin black line that is the reaction product of horeseradish peroxidase, a tracer substance injected intravenously in vivo. The tracer has entered the intercellular spaces of the nonpigmented epithelium (NPC) but is held up by occluding junctions (arrowheads), preventing further progress into the posterior chamber. (X 8450; Courtesy of Dr. Guiseppina Raviola)