But why, it may be asked, do the petals vary in number? Why, for instance, are there 4 in the Muladhara and 6 in the Svadhishthana? The answer given is that the number of petals in any Chakra is determined by the number and position of the Nadis or Yoga-nerves around that Chakra. Thus, four Nadis surrounding and passing through the vital movements of the Muladhara Chakra, give it he appearance of a lotus of four petals which are thus configurations made by the positions of Nadis at any particular centre. These Nadis are not those which are known to the Vaidya. The latter are gross physical nerves. But the former, here spoken of, are called Yoga-Nadis and are subtle channels (Vivaras) along which the Pranic currents flow. The term Nadi comes from the root Nad which means motion. The body is filled with an uncountable number of Nadis. If they were
revealed to the eye, the body would present the appearance of a highly-complicated chart of ocean currents. Superficially the water seems one and the same. But examination shows that it is moving with varying degrees of force in all directions. All these lotuses exist in the spinal columns. The Merudanda is the vertebral column. Western anatomy divides it into five regions; and it is to be noted in corroboration of the theory here expounded that these correspond with the regions in which the five Chakras are situated. The central spinal system comprises the brain or encephalon contained within the skull (in which are the Lalana, Ajna, Manas, Soma Chakras and the Sahasrara); as also the spinal cord extending from the upper border of the Atlas below the cerebellum and descending to the second lumbor vertebra where it tapers to a point called the filum terminale. Within the spine is the cord, a compound of grey and white brain matter, in which are the five lower Chakras. It is noteworthy that the filum terminale was formerly thought to be a mere fibrous cord, an unsuitable vehicle, one might think, for the Muladhara Chakra and Kundalini Sakti. More recent microscopic investigations have, however, disclosed the existence of highly sensitive grey matter in the filum terminale which represents the position of the Muladhara. According to Western science, the spinal cord is not merely a conductor between the periphery and the centres of sensation and volition, but is also an independent centre or group of centres. The Sushumna is a
Nadi in the centre of the spinal column. Its base is called Brahma-Dvara or Gate of Brahman. As regards the physiological relations of the Chakras all that can be said with any degree of certainty is that the four above Muladhara have relation to the genito-excretory, digestive, cardiac and respiratory functions and that the two upper centres, the Ajna (with associated Chakras) and the Sahasrara denote various forms of its cerebral activity ending in the repose of Pure Consciousness therein gained through Yoga. The Nadis of each side Ida and Pingala are the left and right sympathetic cords crossing the central column from one side to the other, making at the Ajna with the Sushumna a threefold knot called Triveni; which is said to be the spot in the Medulla where the
sympathetic cords join together and whence they take their origin—these Nadis together with the two lobed Ajna and the Sushumna forming the figure of the Caduceus of the God Mercury which is said by some to represent them.