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The pineal gland (also called the pineal body, epiphysis cerebri, epiphysis or the “third eye”) is a small endocrine gland in thevertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions.[1][2] Its shape resembles a tiny pine cone (hence its name), and it is located near the center of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join.
The pineal gland was originally believed to be a “vestigial remnant” of a larger organ. In 1917 it was known that extract of cow pineals lightened frog skin. 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.[13] 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.[14]
The secretory activity of the pineal gland is only relatively understood. Historically, its location deep in the brain suggested to philosophers that it possessed particular importance. This combination led to its being a “mystery” gland with myth, superstition and occult theories surrounding its perceived function.
René Descartes, who dedicated much time to the study of the pineal gland,[25] called it the “seat of the soul.”[26] He believed that it was the point of connection between the intellect and the body.[27] The relevant quotation as to Descartes’ reason for believing this is,
My view is that this gland is the principal seat of the soul, and the place in which all our thoughts are formed. The reason I believe this is that I cannot find any part of the brain, except this, which is not double. Since we see only one thing with two eyes, and hear only one voice with two ears, and in short have never more than one thought at a time, it must necessarily be the case that the impressions which enter by the two eyes or by the two ears, and so on, unite with each other in some part of the body before being considered by the soul. Now it is impossible to find any such place in the whole head except this gland; moreover it is situated in the most suitable possible place for this purpose, in the middle of all the concavities; and it is supported and surrounded by the little branches of the carotid arteries which bring the spirits into the brain.[25] (29 January 1640, AT III:19–20, CSMK 143)](http://28.media.tumblr.com/tumblr_ljfbypRH3K1qbrk2fo1_250.jpg)
The pineal gland (also called the pineal body, epiphysis cerebri, epiphysis or the “third eye”) is a small endocrine gland in thevertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions.[1][2] Its shape resembles a tiny pine cone (hence its name), and it is located near the center of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join.
The pineal gland was originally believed to be a “vestigial remnant” of a larger organ. In 1917 it was known that extract of cow pineals lightened frog skin. 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.[13] 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.[14]
The secretory activity of the pineal gland is only relatively understood. Historically, its location deep in the brain suggested to philosophers that it possessed particular importance. This combination led to its being a “mystery” gland with myth, superstition and occult theories surrounding its perceived function.
René Descartes, who dedicated much time to the study of the pineal gland,[25] called it the “seat of the soul.”[26] He believed that it was the point of connection between the intellect and the body.[27] The relevant quotation as to Descartes’ reason for believing this is,
My view is that this gland is the principal seat of the soul, and the place in which all our thoughts are formed. The reason I believe this is that I cannot find any part of the brain, except this, which is not double. Since we see only one thing with two eyes, and hear only one voice with two ears, and in short have never more than one thought at a time, it must necessarily be the case that the impressions which enter by the two eyes or by the two ears, and so on, unite with each other in some part of the body before being considered by the soul. Now it is impossible to find any such place in the whole head except this gland; moreover it is situated in the most suitable possible place for this purpose, in the middle of all the concavities; and it is supported and surrounded by the little branches of the carotid arteries which bring the spirits into the brain.[25] (29 January 1640, AT III:19–20, CSMK 143)
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