The means by which the moon effects ovulation and menstruation has long been attributed to the relationship between the light of the moon and the circadian rhythms of humans.   It makes sense from an evolutionary standpoint that women would synchronize ovulation with the full moon, the time of the greatest available light for festivities and rituals.   The phase of the new moon, where there appears to be no light in the night sky, would correspond to menstruation, or a time to be internalized and inside. Also, there is some correlation to birthrate increasing at the time of the full moon when there is more available light by which to see and work.  

Descartes first discovered the relationship between input of light into the eyes and glandular function.  More specifically, to the glandular function of the pineal gland or what is known in Indian culture as the third eye.  Light information reaches the pineal in the following way:  The retina of the eye contains specialized cells that absorb the light coming in through the lens of the eye.  Upon absorbing the light, the rod and cone cells convert the light energy in the form of anervous impulse.  This impulse is carried for a short distance by the optic nerve.  Then, at the optic chiasma, optic nerves from the two eyes cross, and parts of each go to the opposite side of the brain.  At this point each nerve splits.  Most impulses are eventually sent the optical cortex of the brain, where they are interpreted as vision.  The rest of the impulses…pass back through the brain and down the medulla oblongata, where the brain attaches to the spinal cord.  There the impulses go out of the cord until they reach the two superior cervical sympathetic ganglia, which lie on each side of the neck.  From there the impulses are sent to the pineal gland.  

There is significant documentation that the pineal gland affects several important glandular and organ functions, which influence menstruation, most importantly, the gonads and the thyroid gland.  The pineal gland also generates melatonin and serotonin, which are both influenced by light and darkness exposure.  It is believed that this is the site of physiology where the moon effects the reproductive cycle.  

The endocrine system is mediated in a rhythmic manner by nerve centers in the hypothalamus.  These “super charismatic nuclei” of the hypothalamus function as biological clocks that regulate both the circadian and ultradian rhythms governing a variety of biological processes mediated by the autonomic and endocrine systems.  

The most important effect from nature on the bodies of all life is light.  Light causes patterns of growth in plants, animals and all biological creatures from the sea to the mountains.