Yoga is divided into several branches, ranging from that which teaches the control of the body, to that which teaches the attainment of the highest spiritual development. In the work we will not go into the higher phases of the subject, except when the "Science of Breath" touches upon the same. The "Science of Breath" touches Yoga at many points, and although chiefly concerned with the development and control of the physical, has also its psychic side, and even enters the field of spiritual development.