《Internal Classic》is the earliest medical classic extant in China, its viscera-state doctrine takes five zang-organs, six fu-organs and extraordinary fu-organs as the main bodies and lays a pathophysiological foundation for traditional Chinese medicine. It includes many expositions on the brain and marrow but they scatter in different sections and chapters. A preliminary arrangement of relevant materials is as follows.
The Theory of Marrow in《Internal Classic》
There are two main viewpoints on the knowledge of marrow in《Internal Classic》：
The first viewpoint takes marrow as an extraordinary fu-organ and a viscera-state system parallel with the five zang-organs, six fu-organs, bone, vessels, gallbladder, and uterus. However, marrow differs from bone, vessels, gallbladder and uterus in that it is not hollow and shaping but belongs to a liquiform matter although it contains detained qi and has viscera-like characteristics. Therefore, the view that regards marrow as a visceral organ cannot summarize the characteristics of marrow. This viewpoint is not further elucidated in《Internal Classic》and produces no important influence on later ages.
The second viewpoint is scatteredly seen in many sections and chapters of《Internal Classic》, it takes marrow as a functional system parallel with qi, blood, saliva, body fluid and essence of life and gives a brief exposition on the physiology, pathology and

Author's unit: Guangdong Gaoming Medical and Medicinal Institute of Encephalopathy, 2 Heping Lane, Cangjiang Road, Hecheng District, Gaoming, Guangdong 528500
treatment as well as the nature, formation, classification and distribution of marrow, being the main body of the theory of marrow in《Internal Classic》.
Marrow is a liquiform matter. In《Miraculous Pivot of the Yellow Emperor's Internal Classic》, body fluids are divided into five kinds: namely, urine, sweat, tear, saliva and marrow. Here marrow is regarded as one of the five kinds of secrctions. In《Treatise on Reservoirs》, there is such an account: "A human being has four reservoirs: namely, reservoir of marrow (brain), reservoir of blood (Chong Channel), reservoir of qi (Shanchung) and reservoir of food stuff (stomach). Here marrow is called together with qi and blood. It can, therefore, be concluded that《Internal Classic》takes marrow as a functional system parallel with qi, blood, saliva, body fluid and essence of life. As for the distribution of marrow, the《Treatise on the Importance of the Pulse and the Subtle Skill of its Examination》said: "The bone is the house of marrow"; the 《Treatise on the Formation of the Five Zang-organs》said: "The brain is one of the extraordinary organs where the marrow converges;" and the《Treatise on Reservoirs》said: "The brain is the sea of marrow." It is evident that the marrow fluid is distributed mainly in the bone and the brain.
It is believed in《Internal Classic》that marrow is a refined nutritive substance produced by the kidney essence and food stuff-essence and connected with the brain and that it shares the function of nourishing the bone and tonifying the brain. The《Treatise on Channels and Vessels》said: "With the formation of reproductive essence, the brain and marrow develop." The《Treatise on Primordial Qi in Remote Ancient Times》said: "The kidney controls water metabolism and stores visceral essence," that is, the kidneys preserve vital essence based on which the marrow fluid is transformed. Marrow, as a refined nutritive substance, is of high physiological significance. It nourishes both the skeleton and joints of the whole body and nourishes the brain, the house of intelligence. Only with sufficient supply of marrow fluid can the brain have source of growth and transformation and normal functions. The disease of marrow is frequently found in late stage of illness and is caused mostly by chronic, malignant or late acute febrile disease which impairs the kidney-yin and is in critical stage. The principal pathogenesis of marrow disease is deficiency of the kidney-essence which leads to no source of growth and transformation of marrow fluid. The symptoms are pathological lesions in bone, brain, ears and eyes which are caused by insufficiency of marrow fluid.
For the treatment of marrow disease, the acupoints Paihui and Fengfu are the principal points and based on the theory that marrow derives from the kidney the treatment should be started with tonifying the kidney. On the other hand, invigorating the spleen should not be ignored. Tonifying the kidney and invigorating the spleen are the two main principles of treatment of marrow disease.
The Theory of the Brain in《Internal Classic》
"The brain is the reservoir of marrow", the brain and the marrow are often called together. There are two points of view about the brain: one is that the brain is one of the extraordinary organs where the marrow converges, the other is that the brain is one of the viscera. Although there are no quite detailed descriptions about the brain in《Internal Classic》, the following questions are dealt with briefly:
1. The brain is located in the skull. There is such an exposition in《Treatise on the Importance of the Pulse and the Subtle Skill of Its Examination》: "The head is the house of intelligence", and there is such an account in《On the Prohibitions of Acupuncture》: "Acupuncture of the head hits Naohu."
2. In the era of《Internal Classic》, the importance of the brain was already recognized by the people. In 《Treatise on Channels》,《Treatise on the Twelve Regular Channels》, and《Treatise on Muscle Channels》of《Miraculous Pivot》, there are accounts of association of the brain with limbs and all channels and in《On the Prohibitions of Acupuncture》there is such an account that puncturing into the brain will result in death. The severity of brain injury was already recognized by the people at that time.
3. It can be known by inference from some expositions in《Internal Classic》that the brain was known to control mentality, consciousness and thinking and to be closely related to the seven orifices at that time. It was pointed out that deficiency of primordial energy and insufficiency of brain and marrow can lead to loss of nourishment of the seven orifices with the result that such diseases as poor vision and diplopia develop. The principle of treatment of encephalopathy is basically the same as that of marrow disease.
Relationship Among the Kidney, Marrow and Brain
The principal viewpoints of the brain-marrow theory of《Internal Classic》can be summed up as follows:
1. Marrow is a functional system parallel with qi, blood, saliva, body fluid and essence of life, it exists in bone and brain.
2. The brain is the reservoir of marrow, being a part of marrow and is an organ of vital importance, it has the functions of storing mentality and controlling seven orifices.
3. Treatment of brain-marrow diseases should be based on tonifying the kidney and invigorating the spleen.
Judging from channels and collaterals, the kidney connects with the brain through Foot-taiyang Channel. Physiologically, the kidney is the origin of congenital constitution, preserves vital essence based on which conceptions are formulated, controls water metabolism and stores visceral essence based on which the marrow is transformed. The food essence transported from the spleen and the kidney is to combine with the kidney-essence and is then transformed into marrow fluid. It is evident that the brain connects with the kidney superficially through Foot-taiyang Channel and interiorly through the relationship between kidney-essence, and the transformation of marrow and brain. With sufficiency of kidney-essence and marrow fluid, a normal cerebral and renal function with fullness of energy with visual acuity can be expected; with impairment of the kidney due to congenital defect or protracted or serious disease, the resultant deficiency of kidney-essence will lead to no source of transformation of marrow fluid and hollowness of reservoir of marrow and such abnormal mental symptoms as vertigo and tinnitus develop. To sum up, as early as the era of《Internal Classic》, the importance of the kidney to the brain and marrow was already recognized and tonifying the kidney to replenish vital essence was regarded as the main principle of treatment of brain-marrow diseases.