section_path: Science and technology/Medicine
section_name: Medicine
paragraph_text: Medicine
  
  Han-era medical physicians believed that the human body was subject to the same forces of nature that governed the greater universe, namely the cosmological cycles of yin and yang and the five phases. Each organ of the body was associated with a particular phase. Illness was viewed as a sign that qi, or vital energy, channels leading to a certain organ had been disrupted. Thus, Han-era physicians prescribed medicine that was believed to counteract this imbalance.
  
  For example, since the wood phase was believed to promote the fire phase, medicinal ingredients associated with the wood phase could be used to heal an organ associated with the fire phase. Besides dieting, Han physicians also prescribed moxibustion, acupuncture, and calisthenics as methods of maintaining one's health. When surgery was performed by the Chinese physician Hua Tuo (d. AD 208), he used anesthesia to numb his patients' pain and prescribed a rubbing ointment that allegedly sped the process of healing surgical wounds. Whereas the physician Zhang Zhongjing (c. AD 150 – c. 219) is known to have written the Shanghan lun ("Dissertation on Typhoid Fever"), it is thought that both he and Hua Tuo collaborated in compiling the Shennong Ben Cao Jing medical text.