History of the pineal gland
As an elusive and unique part of the brain, the pineal gland has the longest history among the body organs as a structure of unknown function – it took almost two millennia to discover its biological roles.
[2][3] The ancient Greeks visualised the pineal gland as a sort of guard (valve), like the pylorus of stomach, that regulate the flow of pneuma (vital spirits) in the brain.
According to him, the gland has no spiritual or physiological role, but merely a supporting organ of the brain, and gave the name κωνάριο (konario, often Latinised as conarium) for its cone-shaped appearance.
[9] Herophilus had explained that the structure was a kind of valve, like the pylorus of stomach that controls the amount of food particles moving into the intestine.
[12] In De usu partium corporis humani, he gave the name κωνάριο (konario, often Latinised as conarium) meaning a cone, as in pinecone.
[13] To worsen the misidentification, a 13th-century Dominican scholar, Vincent of Beauvais, at the Cistercian monastery of Royaumont Abbey, France, specifically introduced the Latin name pinea for the memory-conveying vermiform structure, and not the pineal gland.
[18] In his masterpiece, Speculum Maius, he wrote:[Modern translation] Around the middle ventricle there is a part of the brain matter called pinea, which is similar to a worm.
[19]Mondino dei Luzzi, a physician at Bologna, Italy, added to the confusion when he named part of the ventricle as vermis,[20][21] the structure later renamed choroid plexus, but sometimes referred to as vermiform process.
[23] With the revival of the ancient Greeks's notion of the pineal gland, the search for the location of the soul was among the biggest issues in Medieval Christianity.
In his 1664 book, Cerebri anatome cui accessit nervorum descriptio et usus,Willis argued against Descartes' concept, remarking: "we can scarce[ly] believe this to be the seat of the Soul, or its chief Faculties to arise from it; because Animals, which seem to be almost quite destitute of Imagination, Memory, and other superior Powers of the Soul, have this Glandula or Kernel large and fair enough.
[27] Leydig described cup-like protrusions under the middle portion of the brains of European lizards and believing them to be a kind of glands, called them frontal organ (German stirnorgan).
Dermatology professor Aaron B. Lerner and colleagues at Yale University, hoping that a substance from the pineal might be useful in treating skin diseases, isolated and named the hormone melatonin in 1958.
[30] The substance did not prove to be helpful as intended, but its discovery helped solve several mysteries such as why removing the rat's pineal accelerated ovary growth, why keeping rats in constant light decreased the weight of their pineals, and why pinealectomy and constant light affect ovary growth to an equal extent; this knowledge gave a boost to the then new field of chronobiology.
