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, resembles a pine-cone. Physiologists are at sea regarding the function of this strange organ, and generally content themselves with the statement that "its functions are not understood." But occultists know that the pineal gland, with its peculiar arrangement of nerve-cell corpuscles, and its tiny grains of "brain-sand," is the physical telepathic receiving instrument. Students of wireless telegraphy have noticed a startling resemblance between the pineal gland and a part of the receiving instrument employed in wireless telegraphy.