The vibrations arising from emotional excitement are sent out principally from the plexi, or great centres of the sympathetic nervous system.  Those arising from the more strictly mental states emanate from certain centres and points of the brain, or brains, of the person manifesting them.  Certain forms of these vibrations constitute the real essence of what is generally called “human magnetism,” which will be treated upon in the proper place in these lessons.

I do not think it advisable to go into the technical details of the generation and mechanism of transmission of these thought and emotional vibrations, in these lessons.  To understand the same would require a technical knowledge of physiology and organic chemistry, which is not possessed by the average person.  Moreover, such details are neither interesting nor instructive to the general student of occultism.  But, I think it proper to give at least a brief description of the receiving of such vibratory-waves by other individuals.

In the first place, every great plexus, or groups of nerve ganglia, in the human system is a receiving station, as well as a sending station.  A person manifesting strong emotional excitement tends to awaken similar states in the nervous centres of other persons in whom the conditions are favorable.  This explains why the vibrations of anger, fear, panic, are so contagious.  It also explains the strong effect of the vibrations emanating from the nerve centres controlling the reproductive system, in certain cases of strong sexual excitation.  Each human sympathetic nervous system contains many receiving stations where emotional vibrations are received, and where they tend to be transformed into similar feeling in the receiving system, unless neutralized by other mental and emotional states in the person.

When we come to consider the apparatus by which is received the vibrations arising from what may be called “purely mental” operations of the brain, such as intellectual thought, constructive imagination, etc., we find a more specialized arrangement, as might be expected.  There are several minor receiving points of mental vibrations, regarding which I do not consider it worth while to go into detail, because of the technical features involved.  The principal apparatus for receiving thought vibrations of this kind is that which is known as the “pineal gland,” which I shall now describe.

The pineal gland is a peculiar mass of nervous substance which is embedded in the human brain, in a position near the middle of the skull almost directly above the extreme top of the spinal column.  It is shaped like a small cone; and is of a reddish-gray color.  It lies in front of the cerebellum, and is attached to the floor of the third ventricle of the brain.  It contains a small quantity of peculiar particles of gritty, sand-like substance, which are sometimes called “brain-sand.”  It derives its scientific name from its shape, which, as I have said,