Nervous energy is a kind of battery for the whole mechanism of the mind and body. For the mechanism of mind, therefore, it is the clearness of the nervous mechanism and the good working of the nervous mechanism which enable us to make our thought clear to ourselves, or to hold our thought, or to imagine, or to think, or to memorize; and when the nervous system is not clear, then one cannot keep things in mind, conceive things in the mind, or keep to one thought, and various conditions of mental disorder begin to show. Within the body the nervous system is called centers by Yogis. The different centers are the points of the nervous system, the centers through which one experiences intuition, one feels, one observes keenly.