The heat, living between Apana and Prana, in the navel, works, with the help of those two vital airs, in digesting all food that is taken by a living creature.
अपानप्राणयोर्मध्ये प्राणापानसमाहितः। समन्वितस्त्वधिष्ठानं सम्यक्पचति पावकः॥