Why is Huangdi Neijing the earliest medical classic in China?

Huangdi Neijing is divided into two parts: Lingshu and Su Wen. It is the earliest medical classic in China, and it is also one of the four classic works of traditional medicine (the other three are Difficult Classic, Treatise on Febrile Diseases and Shennong Herbal Classic).

Huangdi Neijing is a comprehensive medical work, which establishes the theories of Yin and Yang, five elements, pulse condition, Tibetan image, meridians, etiology, pathogenesis, symptoms, diagnosis, treatment, health preservation and luck. Its basic material comes from the long-term observation of life phenomena in ancient China, a lot of clinical practice and simple anatomical knowledge. It laid the foundation for human physiology, pathology, diagnosis and treatment. It is a medical work with great influence in China and is called the medical ancestor.