A Constructive Survey of Upanishadic Philosophy c6.s2.10

c6.s2.10

this proper physiological explanation of sleep, we find very curious theories held on this point by the sages of the Upanishads. The seer of the Praśna Upanishad holds that sleep is caused by the senses being absorbed in that highest ‘sensorium,’ the mind: “as all the rays of the Sun, O Gārgya, become collected into the bright disc at the time of sunset, and emerge again from it at the time of sunrise, so do all the senses become collected into that highest sensorium—the mind: that is the reason why (in deep sleep) man is not able to hear, nor to see, nor to smell. People say about him that he has slept.” (S. II. a). This same seer qualifies his statement a little further, and says that the reason of the deep sleep is that the mind is merged into an ocean of light: “and when he is overpowered by light, then does this god (Soul) see no dreams, and at that time great happiness arises in the body.” (S. II. b). Another theory which is advanced in the Chhāndogya Upanishad is, that sleep is caused by the soul getting lodgment in the arteries: “When a man is fast asleep, and being happy knows no dreams, then his soul has moved in the arteries.” (S. II. c). This same idea is elaborated in the Bṛihadāraṇyaka Upanishad, where a physiological explanation, which in the light of modern science appears almost a mythological explanation, is offered according to the ancient ideas. It was imagined that the heart sent forth about 72,000 arteries to the ‘Purītat’, which Deussen translates as ‘perikardium’, and which Max Müller, following the commentator, wrongly translates by ‘the surrounding body’. This Purītat corresponds to the pineal gland of Descartes, so far as function is concerned; but it differs from it in its anatomical location. The Purītat must be considered as meaning a kind of membraneous sac round the heart. It was imagined by those ancient seers, that in deep sleep the soul moved from the heart by means of the arteries and got lodgment inside the Purītat, whence sleep followed. This same idea was later developed in the Nyāya philosophy where sleep was explained as being due to the moving of the soul right inside the Purītat, the state of dream being explained as due to the soul's position just on the threshold of the Purītat—the soul knocking for entrance inside it,—while it was imagined that during the waking state the soul kept moving from the heart to the Purītat. The origin of this doctrine in the Nyāya philosophy is to be traced to the passage in the Bṛihadāraṇyaka which we are at present discussing: "When a man is fast asleep and when he is not conscious of anything, his soul moves by means of the arteries, called Hitāḥ, which are 72,000 in number, and which are spread from the heart to the Purītat; there he sleeps like a youth, or a great king, or a great Brahmin who has reached the summit of happiness." (S. II. d).