The Chinese relied on traditional herbal medicine for proper balance of the qi, the essential life force. Apothecaries balanced qi by making sure that the liver, heart, spleen, lungs and kidneys, corresponding with the five elements of wood, fire, earth, metal and water, were balanced with the six essences - wind, cold, heat, dampness, dryness and fire. A body out of balance was weakened and susceptible to disease and illness. Apothecaries relied on herbs, animal and insect parts, minerals, fruits and other plants to maintain health. Acupuncture, the insertion of needles into meridians in the body, was also used.