Blood, circulating in the vessels, is a red liquid substance rich in nutrients. It is one of the indispensable substances that constitute the human body and maintain its life activities. Blood originates from cereal essence 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 long-term malnutrition or a lasting hypofunction of the spleen and stomach 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 spleen and the liver. The heart-qi is the 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 movement 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, dysmenorrhea or amenorrhea in women.

Blood circulates within the vessels, by which it is carried to the zang-fu organs 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, 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 normal, the tendons and the bones are strong and the joints are nimble.” Thus, it can be seen that the sensation the 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 from normal circulation and a sufficient supply of blood. So any blood trouble, whatever the causes maybe, will bring about symptoms of mental activities varying in degrees. Basic Questions advises people: ” Qi and blood are the foundation for 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,
Body fluid is called jinye in TCM, including all kinds of fluids in the organs and tissues and their secretions, such as gastricjuice, intestinal juice, nasal discharge, tears, sweat, urine and so on. Just like qi and blood, body fluid is also one of the essential substances constituting the human body and maintaining its life

jin and ye are always mentioned in the same breath because of the fact that, for one thing, both of them derive from food and water transported and transformed by the spleen and stomach. and for another, they can transform into each other. But they are actually different in thickness, property, function and distribution. By and large, jin is the fluid which is clear and thin and flows easily. It is distributed in the skin, muscles and orifices, furthermore, it permeates the blood vessels to keep them moistened. Ye, on the contrary, is thick fluid with flowing less easily. It is distributed in the joints, brain, marrow and internal organs to nourish them. Jin and ye may transform into each other. These two fluids are hard to be separated completely and, for this reason, they are jointly referred to as “jinye” (body fluid) . In case of the impairment of jin or exhaustion of ye, the two must be identified in TDS.

The formation, distribution and excretion of body fluid are the complex physiological process in which they are accomplished by the joint action of many organs. As is pointed out in Basic Questions : “After food and drink enter the stomach, they are digested and transformed into food essence and then, transmitted upward to the spleen, which disperses the essence upward to the lung and the lung regulates water pathways downward to the urinary bladder. And by doing so body fluid is finally disseminated to all parts of the body along all the meridians and collaterals. ” This description suggests that, 1) body fluid is formed from food and water by digestion and absorption of the stomach, separating the clarity from the turbidity of the small intestine and tramformation of the spleen; 2) the distribution and excretion of body fluid are accomplished by the joint action of many zang-fu organ, such as the transforming function of the spleen, the dispersing and descending function of the lung, the steaming and ascending function of the kidney; and 3) body fluid takes triple energizer as its passageway for distribution and excretion.

Body fluid bears two physiological functions: moistening and nourishing：body fluid distributed to the body surface moistens and nourishes the muscles and skin with hairs; body fluid permeated through the body orifices moistens and protects the eyes, nose，mouth and other openings; body fluid infiltrated into the blood vessels nourishes and smooths them and is also the basic component of blood; body fluid poured into the internal organs nourishes and moistens them, and body fluid in the bone nourishes and moistens the bone marrow, spinal cord and brain marrow.