Blood, circulating in the vessels, is a red liquid substance rich in nutrients. It is one of the indispensable substances that constitute the hunan body and maintain its life activities. Blood originates from cereal esence transformed by the spleen and stomach, and has the functions of nourishing and moistening the whole body.

Nutritive qi and body fluid are thought of as the material basis of blood formation. As both of them derive from cereal essence, the quality of the food intake and the conditions of the spleen and the stomach are bound to have a direct bearing on blood formation. Either a kong-term malnutrition or a lasting hypofunction of the splcen and stornach may cause insufficient blood formation, resulting in blood deficiency. That's why TCM states *Reinforcing the spleen and the stomach enables blood to develop spontaneously.

Normal blood circulation comes of the joint action of the heart, the lung, the splen and the liver. The hear- qi he fundamental motive power to propel blood circulation. The lung is in charge of qi of the whole body and, therefore, has an important bearing on the formation of zong qi. When zong qi gets in the heart meridian, it may promote the tmovement of qi and blood.

The spleen may keep blood flowing within the vessels and prevent it from extravasating. And the liver, besides its function of storing blood, adjusts the volume of blood flow and maintain the normal flow of qi and blood. In case any one of the above organs fails to work properly, abnormal blood circulation is certain to occur. The heart-qi deficiency, for instance, may lead to heart-blood stagnation. The spleen-qi deficiency fails to control blood, leading to bleeding, etc. The disturbance of qi flow of the liver and blood circulation may bring about such pathological changes as blood stasis or swelling, abnormal menstruation, dystmenorrhea or amenorrhea in women.

Blood circulates within the vessels, by which it is carried to the zang-fu ongans internally and to the skin, muscles, tendons and bones externally. It circulates ceaselessly Like a ring without end to nourish and moisten all the organs and tissues. In this way, normal physiological activities are maintained. Basic Questions says: "The liver with blood is able to ensure normal vision; the feet with blood are able to walk; the palms with blood are able to grip things; the fingers with blood are able to grasp". "When discussing the relationship. between blood and the tendons, the bones and the joints, Miraculous Pivot points out: "When blood is nornal, the tendons and the bones are strong and the joints are nimble." Thus, it can be seen that the sensation and the movement of the body never for a moment deviate from the nutrients provided by blood.

Blood is also the material basis of mental activities. Sound mental activity results fron normal circulation and a sufficient supply of blood. So any blood trouble, whatever the causes may be, will bring about symptoms of mental activities varying in degrees. Basic Questions advises people: "Qi and blood are the foundation fot human mental activities and have to be nursed with caution." And Miraculous Pivot informs us, "Harmonious blood vessels ensure a vigorous spirit." These famous remarks show the close relationship between blood and mental activities. Deficiency of blood, therefore, will cause mental disorder. For example, heart-blood or liver-blood deficiency wil lead to such symptoms as palpitation, insomnia and dreaminess.