by Sri Swami Sivananda

The physical body is shaped in accordance with the nature of the astral body. The physical body is like water in its gross form. Water that is heated becomes vapor. Vapor could be compared to the astral body. The astral or subtle body is within the gross body. The physical body cannot function without the astral body. Each gross center of the body has its corresponding astral center.

Chakras are centers of spiritual energy. They are located in the astral body, but have corresponding centers In the physical body. There are seven important chakras. They are: the Muladhara, situated at the anus; Swadhishthana, at the genital organ; Manipura, at the navel; Anahata, at the heart; Vishuddha, at the throat; Ajna, at the space between the eyebrows; and the Sahasrara, which is located at the top of the head.

Corresponding to the chakras in the astral body, there are plexuses in the physical body. A plexus is a center of interwoven nerves, arteries, and veins. The sacral plexus corresponds to the Muladhara chakra; prostatic plexus to Swadhishthana chakra; solar plexus to the Manipura chakra; cardiac plexus to the Anahata chakra; laryngeal plexus to the Vishuddha chakra; and cavernous plexus to the Ajna chakra.

Each chakra has control over a particular center in the gross body. The nervous, digestive, circulatory, respiratory, and genito-urinary functions, as well as other systems of the body, are under the control of the chakras. The gross nerves and plexuses of the physical plane have a close relationship with the subtle ones. As the physical centers are closely related to the astral centers, the vibrations that are produced in the physical centers by prescribed yogic methods have the desired effects in the astral centers.


The chakras are located in the Sushumna, the main nadi of the astral body. Nadis are astral tubes made up of astral matter that carry psychic currents. The Sanskrit term, “nadi,” comes from the root, “nad,” which means “motion.” It is through these subtle tubes or passages that the vital force flows. As the tubes are made of subtle matter, they cannot be seen with the naked eye, nor can they be subject to any scientific experiments conducted on the physical plane. These yoga nadis are not the ordinary nerves, arteries, or veins known to anatomists or physiologists.

The source of all nadis, an egg-shaped center of nerves called the Kanda, is situated between the anus and the root of the reproductive organ. It lies just above the lowest chakra. The Kanda is a center of the astral body from which the subtle channels spring and carry the vital prana to the different parts of the body. Corresponding to this center is the cauda equina in the gross body. The spinal cord, extending from the brain to the end of the vertebral column, tapers off to a fine silken thread. Before its termination, it ramifies into numerous fibers. This fibrous network is called cauda equina in the gross body. The Kanda is the astral center of the cauda equina.

The human body is filled with innumerable nadis. Estimates on the number of nadis range from 72,000 to 3,500,000. Of these, seventy-two are commonly known. Of the seventy-two, there are ten chief ones which carry the prana.

The three most important nadis are the Sushumna, Ida, and Pingala. The Sushumna is the main one, the highest and most sought after by the yogis. The other nadis are subordinate to it. The Sushumna extends from the Muladhara chakra to the opening in the crown of the head. Western anatomy recognizes a central canal in the spinal cord, called the canalis centralis. It is made up of grey and white brain matter. Just as the spinal cord is suspended in the hollow of the spinal column, the Sushumna is dropped within the spinal canal.

There are two nerve currents, one on either side of the spinal column. The left one is called Ida and the right is known as Pingala. They are the subtle nadis that carry the subtle prana. In the physical body, these correspond to the left and right sympathetic chains. Ida flows through the left nostril and Pingala through the right. Ida cools and Pingala heats. The breath flows through the left nostril for one hour and then through the right nostril for one hour. Man is busily engaged in worldly activities when the breath flows through Ida and Pingala. Only when the mind is concentrated and controlled and all its thought-waves have subsided, does the Sushumna function. Then the breath flows simultaneously through both the nostrils. When prana moves in the Sushumna, there is deep meditation, and the yogi enters into samadhi.

The purification of the nadis is important. If there are impurities in the nadis, the ascent of the Kundalini in the Sushumna is seriously retarded. Pranayama brings about quick purification of the nadis, and purity of the nadis facilitates the ascent of the Kundalini.

When the nadis have become purified, certain external signs appear on the body of the yogi. They are: lightness and leanness of the body, brilliancy in complexion, increase of the gastric fire, and absence of restlessness in the body. They are all signs of purification.


Kundalini, the serpent power and the mystic fire, is the primordial energy, the Shakti that lies dormant in the Muladhara chakra. It is an electric, fiery, occult power – the great pristine force that underlies all organic and inorganic matter. It is the cosmic power in individual bodies. It is not a material force. It is the spiritual potential of the cosmic power.

When the Kundalini Shakti is awakened, it passes from the Muladhara chakra to the Sahasrara through all the chakras. When the Kundalini travels from chakra to chakra, layer after layer of the mind opens and the yogi acquires psychic powers. He obtains control over the five elements. When it reaches the Sahasrara chakra, he is in the realm of limitless knowledge and enjoys supreme bliss.

Serve, Love, Give, Purify, Meditate, Realize.

– Sri Swami Sivananda Maharaj