nerve branches with nerve endings and receptors distributed in the foot (Fig. 2-22) to conduct nerve impulses to and from the brain for fast adjustments to bodily conditions and changes in the external environment. The eyes and balance organs in the inner ear also contribute to these adjustments.

There is a thick plantar cushion in the sole of the foot covered with a dense layer of epithelium and laid over a thick pad of fat. The arch of the foot (Fig. 2-23) is a unique construction in human beings, an evolutional product of the human body allowing it to stand erect and

1-gravity line 2-transverse arch of foot 3-plantar arch (lateral and medial longitudinal arches of foot)

walk. The bones, joints, and ligaments of the foot are arranged in a bow-like arch with an upward convex curvature to form the elastic structure of the arch. The rebound force from the ground when walking, jumping or bearing heavy weight is thereby diverted and reduced by the arch of the foot to protect the internal organs and tissues from injury. It also protects the nerves and blood vessels in the sole when standing or bearing weight for a long time. The arch consists of the longitudinal arch, anteroposteriorly arranged, and the transverse arch, mediolaterally arranged. To protect the arch of the foot, physical exercise is recommended to strengthen the foot muscles, ligaments and bones. Standing in a static posture over a long time should be avoided. Walking, running and jumping capability may be severely impaired in patients with flat feet.

The foot has been called a "second heart" or "third eye" of the human body because it can play a role in adjusting essential body organs such as the heart and eye through the close connection between the foot and the internal organs. As with the hand, the electrical activity of the foot is very similar to that of the head. The foot is sensitive to changes in temperature and can rapidly affect the functioning of the respiratory, circulatory, and digestive systems. There is a folk proverb: "The whole body feels warm if the foot is warm, and the whole body feels cool if the foot is cool." The aging process, bodily instability, and many diseases often start in the lower limbs. The head, hands and feet are similarly distant from the anatomical and gravitational center of the body. Therefore, an important function is particularly committed to these "periperal structures" of the body.