Harderian Gland

HARDERIAN GLAND (Harder), first described in 1694 by Basel professor Harder in a deer, is located in the orbit cavity between its medial wall and the eyeball. Its anterior part lies adjacent to the third eyelid, or nictitating membrane. Its duct opens either on the inner or outer surface of the latter. The Harderian gland is found only in rodents, some insectivores, and certain ungulates (pig, deer). Previously, all glands located in the medial corner of the orbit were called Harderian glands. However, it was later established that in addition to the Harderian gland, the so-called 'nictitating gland' (Nickhaut-drüse) is also located in this place, which in structure resembles the lacrimal glands and is completely different from the Harderian gland. The Harderian gland has a tubular or alveolar-tubular structure and secretes a lipid substance with a significant cholesterol content. In rabbits, the Harderian gland consists of two parts: a white part containing anisotropic fat droplets, and a pink part containing isotropic fat droplets. The relatively large size (in rabbits up to 2 cm in length and 1-1½ ^cm in width) and significant weight of the Harderian gland (in rabbits on average up to 3.6 g, i.e., heavier than the adrenal glands and ovaries) led to the assumption that it has some important function, not only local but also of general significance. Recent research (Walter, E. Moiseev) has shown that the Harderian gland plays a significant role in lipid metabolism, specifically as an organ that excretes lipids from the body. When fed lipids (cholesterol), the Harderian gland increases in volume and weight, and the lipid content in it increases significantly. However, in contrast to the adrenal glands, the Harderian gland is not a depot of lipids, but merely an organ that constantly excretes them outward. When the Harderian gland is removed on one side, compensatory hypertrophy occurs on the other. During starvation, the Harderian gland loses weight relatively much less than the rest of the body. The Harderian gland is essentially one of a series of skin glands with lipid secretion, especially developed in rodents. These also include the anal, preputial, sebaceous, and Meibomian glands, which apparently, in addition to their local function, also have a general significance for lipid metabolism.