The human pineal organ is a minute gland (approximately 150 mg) that projects from the diencephalon into the third ventricle. Being in that ventricle, the pineal gland is in direct contact with the cerebrospinal fluid [Welsh, et al., 1989]. The cerebrospinal fluid is considered by bioenergy workers to be the carrier of information and life energy that is received by the organism and is then distributed throughout the body [Still, 1902; Stone, 1987; Sutherland, 1990]. The pineal gland is located in the exact center of the brain. It is the first gland to be formed in the body and, according to Reiter [Reiter, 1995], it is clearly distinguishable at three weeks after conception. Other sources place the creation of the pineal gland at five to seven weeks [Strassman, 1990].

The pineal gland has received attention from prominent philosophers and mystics for more than 2,000 years.

In the Oriental world, where there has long existed a deep interest in and understanding of the connection between psychic phenomena and a personís physical state, it is believed that all psychic systems have a corresponding organ in the physical body where activity in the psychic system is reflected [Roney-Dougal, 1991]. The physical equivalent of both the "third eye" energy center (brow chakra) and the crown energy center is the pineal gland. The pineal gland, according to the Oriental mystics, is said to be the receptor and sender of subtle vibrations which carry thoughts and psychic phenomena throughout the body and which connect us to universal, "cosmic" energy. Ryerson [Davidson, 1988] describes the pineal gland as "a crystalline structure that is an integral controlling part of the interface between the body and higher subtle energies." There is a state of vibratory resonance along the length of the spinal column, from the medulla oblongata to the coccyx. Information received from subtle energy fields via the pineal gland is encoded and transmitted along the spinal column as a resonating vibration. The information travels to other parts of the body through energy pathways, bioelectrical fields, nerve fibers, and circulatory systems.

In the Western world, the 17th Century philosopher, Rene Descartes, in his religious, philosophical, and psychological works, noted the that the pineal gland is the only unpaired organ in the brain, and that it is located in brain's center. Descartes described the psychological function of the pineal gland to be analogous to a valve that controls the flow of thought to consciousness. He saw the cerebrospinal fluid as the carrier of thought. On an esoteric level, Descartes identified the pineal gland as an organ through which the soul operates in the body. He also hypothesized that, in addition to using the cerebrospinal fluid, the pineal gland sent its messages through nerves and the blood [Wheelbright, ed., 1954]. These conjectures were made by Descartes three centuries before the identification of melatonin! After the work of Descartes, the pineal gland received little attention until the mid-20th Century. The modern renewal of interest in pineal science was marked by the work of Mark D. Altschule in the early 1940s. He had uncovered and called attention to 17 papers, all published since 1880, that described the use of pineal gland extracts in the treatment of mental illnesses [Kitay and Altschule, 1954; Brainard, 1978]. The discovery of melatonin by Lerner in 1958 [Reiter, 1995] identified the pineal's primary hormonal agent. This opened the door to scientific study of the physiological effects that had been signaled by Altschule. The scientific view of the pineal gland changed from its being a functionless vestigial organ to an actively functioning neuroendocrine transducer—an organ that converts a neural signal conveying environmental information into an endocrine message [Brainard, 1978; Vollrath, 1984; Zawilska et al., 1992, 1996; Nowak and Zawilska, 1996, 1997].

It is now clear to scientists that the pineal gland (by means of its neurohormone messengers) has a profound effect on many aspects of human functioning and plays a key role in enabling people to live in harmony with environmental rhythms.

Melatonin is the principal hormone secreted by the pineal gland, its "biochemical messenger", a "three billion year-old molecule" [Reiter, 1995]. It appeared very early in the course of evolution [Reiter, 1995; Turlejski, 1996]. It can be found in a great variety of life forms, including algae. The most notable feature of the melatonin generating system is that it follows a circadian rhythm.

The recent research that studies the pineal gland and melatonin synthesis is extensively presented in scientific journals. For that reason, only those aspects of the melatonin generating system that are pertinent to the author's research in autism will be described here, and that will be done very briefly. The pathway for the creation of melatonin is as follows: light - retina - retinohypothalamic track - suprachiasmic nucleus - paraventicular nucleus - midbrain - spinal cord - superior cervical ganglion (SCG) - postsympathetic fibers - pineal

The SCG sends fibers containing the neurotransmitter norepinephrine to stimulate noradrinergic receptors on the pineolocytes. It is the activation of these receptors that begins the enzymatic process which leads to the synthesis of melatonin, the main pineal secretion.

Melatonin is synthesized from dietary L-tryptophan which enters the pineolocytes and is converted to melatonin through the following pathway: L-tryptophan - 5-hydroxytryptophan - serotonin - N-acetyl-serotonin - melatonin

The enzyme serotonin N-acetyl-transferase [NAT] which converts serotonin to N-acetyl-serotonin is the rate limiting enzyme in this process. HIOMT is the enzyme which converts N-acetyl-serotonin to melatonin.

For the proper functioning of the melatonin generating system, an intact neuronal pathway must be present as well as a properly functioning pineal gland. The pineal gland has a weak regenerative system due to its neuronal derivation [Grad, et al., 1993]. The number of pineolocytes is genetically determined, and the ones that are destroyed cannot ordinarily be replaced in post-natal life. With a continuing loss of pineolocytes, a state of pineal failure will eventually be reached [Reuss et al., 1986; Reuss, 1990]. Studies carried out on humans indicate that the ability of the pineal gland to produce melatonin decreases with age [Grad et al., 1993; Reiter et al., 1980; Pang et al., 1984; Waldhauser et al., 1988; Nowak and Zawilska, 1996, 1997]. Calcifications in the pineal have been shown to occur throughout life [Welsh, 1985]. Stress has been shown to have an effect on pineal hormonal functioning [Grad et al., 1957; Miline et al., 1970; Korn, 1997].

Generally speaking, disturbances in pineal metabolism and a decline in the output of melatonin can be caused by reduced sympathetic, parasympathetic, and CNS innervation, vascular atrophy, and replacement of functional with nonfunctional tissue in the pineal. Malfunctioning of the pineal gland and restrictions in the SCG pathway will be discussed later in this paper as possible causes of autism. Of the many functions performed by and connected with the pineal gland and its neurochemical messenger, melatonin, only a few will be discussed here, i.e. those believed to be related to malfunctioning systems in autism