Ida, the Lunar Channel

The nadis are, in the yogic and tantric physiology of India, the channels through which the vital energy, prana, flows in the subtle body; the texts speak of thousands of them, but three are principal, and Ida is one of the two that spiral around the central channel. Ida is the lunar channel, cool, receptive and associated with the left side, with the moon, with the parasympathetic calming functions and with the mental and introspective aspects of the self.

In the classic description it winds from the base of the spine up to the region of the left nostril, crossing the central Sushumna and alternating with its solar counterpart Pingala at the energy centres. The breath is said to flow more strongly through one nostril and thus one channel at a time, alternating through the day, and much yogic breath-practice aims to balance the two so that energy can enter the central channel. The nadi doctrine is ancient, part of the tantric and hatha-yoga subtle anatomy set out in texts such as the Hatha Yoga Pradipika.