शतं चैका च हृदयस्य नाड्य-
स्तासां मूर्धानमभिनिःसृतैका ।
तयोर्ध्वमायन्नमृतत्वमेति
विष्वङ्ङन्या उत्क्रमणे भवन्ति ॥ १६॥
śataṃ caikā ca hṛdayasya nāḍya-
stāsāṃ mūrdhānamabhiniḥsṛtaikā .
tayordhvamāyannamṛtatvameti
viṣvaṅṅanyā utkramaṇe bhavanti .. 16..
There are one hundred and one arteries of the heart, one of which pierces the crown of the head. Going upward by it, a man at death attains immortality. But when his prana passes out by other arteries, going in different directions, then he is reborn in the world.
Commentary:
One hundred and one nerve currents are said to emanate from the centre of the heart. There are millions of nerve currents, but the main ones are one hundred and one. Tāsām mūrdhānam abhiniḥsṛtaikā: Among these nerve currents which are spread out throughout the body, one rises to the crown of the head. Tayordhvam āyann amṛtatvam eti: If the jiva departs through this central nerve current, called the sushumna, through the crown of the head, one attains immortality. Viṣvaṅṅ anyā utkramaṇe bhavanti: But if the prana departs horizontally or inversely through the lower parts of the body, there will be rebirth.
The belief is that if the prana departs through any aperture above the neck, there will be no rebirth. It can depart through the nostril or the ear or the mouth; or if it departs through the brahmarandhra, it means final salvation. And even if it is through the mouth, it may go to some region such as Brahmaloka, etc. But if the prana passes through any other horizontally moving nerve or downward moving current of the nerve, there will be rebirth in some realm or the other. So work has to be carried on through the practice of yoga by eliminating the circumstances which may make the nerve currents flow transversely or horizontally. They take that zigzag movement because of desires, which are horizontal.
All our desires are horizontal movements; they do not go vertically. They move to the front, to the rear, to the right, to the left, in the direction of objects. Because of the externality, the horizontality of the objects of attraction, the nerve currents and prana also move in that direction and compel us to take birth in this very world of objects. But if our consciousness rises up through the concepts of higher and higher dimensions of reality to the realms of being which are above, until we reach Brahmaloka and the Absolute, then the prana will push the consciousness through the sushumna nadi and pierce the brahmarandhra. There are some people who break the head with a coconut at the time of death—or sometimes they break the coconut only, just to give a semblance of the apparent movement of consciousness through the current of the head.