Tantric theories about the chakras are based very much on the traditional religious concepts and iconography of that particular culture.  A much freer interpretation of the chakras was introduced in the West by the Theosophists, beginning with C. W. Leadbeater, in his books The Inner Life and The Chakras. (the latter being the source of the above illustration).  The latter book incidentally, first published in 1927, has since sold more copies than any other Theosophical book.  In these books Leadbeater makes several important and original observations, which have been followed by almost all subsequent theosophical and New Age writers and clairvoyants, although very few actually give him credit for being the first to come up with these ideas.

According to this understanding, the chakras can be perceived through psychic vision, or Clairvoyance (French: "clear seeing").  This is something quite different from what we find in Tantra.  In Tantra, especially Tibetan Tantra, the yogi "creates" the chakras as part of his mental exercises; a sort of stylised yogic visualisation.  But the Theosophical and New Age idea of clairvoyance implies that the chakras have an independent objective existence in the subtle bodies that can be perceived by anyone who has developed the appropriate faculties.

According to clairvoyant perception, the chakras are seen as energy vortexes in the each of the subtle bodies.  This again is quite different to the Indian, Tibetan, and other traditions, where the chakras are subtle centres of consciousness, but have no energy-status of their own.

Leadbeater was also the first to suggest that the chakras are energy/consciousness transformers, linking the various subtle bodies (the etheric body, the astral body, the mental body, etc) by stepping down the frequency of the consciousness-energy of the higher body, so it can be received by the lower one.

Most esoteric writers now also seem to agree that the chakras are energy/consciousness receivers and transmitters that enable the person to assimilate the cosmic vitality that is so necessary for well-being.  Emphasis therefore is placed on the health of the chakras; whether they are open or closed, blocked or clear, rotating clockwise or anti-clockwise.

Each of the chakras is also associated with particular endocrine glands and ganglions or plexii in the sympathetic nervous system; the idea being that the subtle workings of the chakras are related and repeated in the physical body through the activity of the various glands and nerve plexii.  Although Woodroffe and various contemporary Hindu writers made some contributions here, it was the theosophists such as Leadbeater and Alice Bailey who actually fixed this idea as dogma.  Locating the chakras at specific vertebrae is also a relatively recent idea; the original Tantric writers may have lacked the anatomical knowledge to make precise statements such as this.  But it is also a fact that despite modern knowledge, contemporary writers often disagree over the exact positions of the chakras.  The Manipura for example is sometimes located in the navel (the Tantric positioning) and sometimes in the Solar Plexus.

The idea of the spleen chakra was taken up by Alice Bailey (or her source, "the Tibetan"), and through both her and Leadbeater became established as "fact" within the general theosophical occult-esoteric world-view.

Chakren by Alfred Ballabene, - material in German on Leadbeater, Gichtel, and general theosophical conceptions of the chakras