The ultrastructure of conjunctival nerve fibres was studied in control material from two species of monkey. Nerve fibres reached the conjunctiva either in small nerves or in the adventitia of arterioles. A few myelinated nerve fibres were found within the nerves but the great majority of their fibres were unmyelinated. Bundles of unmyelinated nerve fibres were found in the interstices of the lamina propria up to the epithelial basement membrane and nerve fibres were traced into the epithelium. Other unmyelinated nerve fibre bundles lay adjacent to the walls of capillaries. Nerve fibre terminals exhibited varicosities and three types of terminals were recognised; those having varicosities packed with mitochondria, those having varicosities containing vesicles without any small granules and those having varicosities with vesicles, some with small granules.

Following experimental nerve lesions induced changes were observed in the nerve fibres, and from these changes it was determined that nerve fibres from three sources were present in the conjunctiva. Nerves and interstitial nerve fibre bundles contained ophthalmic and pterygopalatine nerve fibres, from which the epithelium was supplied. Arteriolar nerve fibre bundles contained superior cervical and pterygopalatine nerve fibres which were joined by ophthalmic nerve fibres in capillary nerve fibre bundles.

The combined results of electron-microscopy of control and experimental material suggested that nerve fibres from different sources innervating the conjunctiva had ultrastructurally distinct terminals.