The Apana air, becoming the lord, on account of such lordship over it, makes it at one with itself. That restrained motion of the Prana air has been said to be the motion of the mind. Hence the mind depends upon Prana.
ब्राह्मण उवाच तामपानः पतिर्भूत्वा तस्मात् प्रेषत्यपानताम्। तां गतिं मनसः प्राहुर्मनस्तस्मादपेक्षते॥