1-nail base 2-nail bed 3-nail 4-fibrous bundle 5-blood vessel of finger 6-phalan-geal bone, 7-nerve 8-fibrous septum

The construction of the palm is compact, while the dorsal skin of the hand is thinner and its subcutaneous tissue is looser to allow flexible hand movement. The dorsum of the hand is arrayed with numerous veins and nerves to enable the hand to carry out its delicate functions.
With its complex structure the hand can performs various delicate and nimble movements under the control of the brain. According to experimental study, the hand shows a variation of cutaneous electrical activity similar to that of the brain. The mechanism of this similarity between the brain and hand is still unknown, but it demonstrates the specificity of the hand. The hand's tolerance for mechanical strain, its sensitivity to environ-mental changes of temperature and humidity, and its range of self-adjustment are all very remarkable. The complicated structure, functions, and physiological reflexes of the hand are the foundation of its skilful and dexterous activities.

2. Basic principles of acupoints and reflecting areas on the hand:
According to traditional medical theory of the meridian, a mutually connected and crisscrossing network is present in the body as an endless circuit connecting the internal organs and the external limbs. However, according to modern concepts this is a nervelike channel system, temporarily composed of cells, connecting the external and internal structures and adjusting the functions of the entire body. There are 12 regular meridians, and they originate from or stop at limb terminals. Six of these meridins are the hand meridians including the hand Taiyin lung, hand Yangming large intestine, hand Jueyin pericardium, hand Shaoyang triple energizer, hand Shaoyin heart, and hand Tai-yang small intestine meridians. The acupoints and areas on the regular meridians are called regular acupoints, and there are 23 regular acupoints on the hand, 9 on the palm, and 14 on the dorsum of the hand.

With the development of medical practice, people discovered more and more acupoints and their specific therapeutic effects, although they are not located on the meridians. These are called extra acupoints, and there are 77 extra acupoints on the hand, increasing the available locations for the application of therapeutic stimulation.