S.J. Rehorek, W.J. Hillenius, W. Quan, and M. Halpern.
Canadian Journal of Zoology, In Press (2000).

Abstract: The Harderian gland is a poorly understood structure, found in the anterior orbit of most terrestrial vertebrates. In Thamnophis spp. (Serpentes: Colubridae), it is a seromucous secretory glandular structure, with a large post-orbital portion. Numerous functions have been ascribed to this gland, including contibutions to orbital lubrication or the vomeronasal system. Anatomically, the Harderian gland is connected to the VNO via the nasolacrimal duct. In this study, we traced the serous secretions of the Harderian gland using autoradiographic techniques at the light microscopic level. We injected the Harderian gland of snakes with ³H proline either unilaterally (right side) or bilaterally. The right Harderian glands of both treatment groups were then injected with a potassium rich solution. The right-sided Harderian glands exibited labeling in the Harderian gland, Harderian gland ducts, nasolacrimal duct, VN sensory epithelium, VNO lumen and vomeronasal duct. No such labeling was observed in any of the other treatments examined. Additionally, since no labeling was observed in the orbital space, we concluded that the serous secretions of the Harderian gland in Thamnophis spp. does not function in orbital lubrication. Thus, the serous secretions of the Harderian gland in snakes flows to the VNO, and may be considered part of the vomeronasal system. Whether this is the source of the fluid layer covering the vomeronasal sensory epithelium remains as yet to be determined.