ABSTRACT
The lacrimal apparatus may be divided into secretory and excretory components. The secretory components consist of the orbital lacrimal gland, the third eyelid gland, and the glands of the eyelids. Cows, pigs, birds, and rodents have an additional deeper gland in the third eyelid, the Harderian gland1, the secretions of which are high in lipids2. In general, the gland is absent from terrestrial carnivores and primates. The excretory components of the lacrimal system consist of a lacrimal
puncta on each eyelid (in most domestic species), a lacrimal canaliculus draining the punctum into the lacrimal sac, and the nasolacrimal duct (9.1).
