The Regulation of Life Activities by the Manas

All changes, movements, and activities of the physical body fall within the scope of the aggregate of volitional formations; they are directly regulated by the manas, with the body consciousness and mind consciousness participating, but not necessarily involving the mind consciousness's deliberative analysis and directive function. When the manas grasps these activities as self and as belonging to self, that is the view of self (satkāya-dṛṣṭi). External activities of the body necessarily involve the participation of the mind consciousness and body consciousness. For example, when walking along a relatively familiar stretch of road, without the mind consciousness's deliberation and direction, the manas can lead the mind consciousness and body consciousness to complete that stretch of road; but if that stretch of road is unfamiliar, the manas must rely on the mind consciousness's deliberative analysis and guidance in order to lead the mind consciousness and body consciousness to complete that stretch of road.

However, the autonomous activities of the physical body's organism—such as the activities of the internal organs, the heartbeat, the pulse, gastrointestinal peristalsis, the metabolism of cells and tissues, the growth of nails and hair, changes in tissue structure, the growth and changes of muscles and bones, and so on—are not regulated by the mind consciousness or the manas; they all change in accordance with karmic seeds and karmic conditions, being the sustaining activities carried out by the tathāgatagarbha upon the living organism in accordance with karmic seeds and karmic conditions.