His changes

• He said diseases came from the outside of the body, and rejected the four humours theory.
• He diagnosed his patients by observing them in person.
• Observed and recorded patient symptoms closely. (clinical observation)
• Studied classified and wrote detailed descriptions of diseases. E.g. Scarlet fever.
• He treated diseases as a whole, not separate symptoms.
• He use mild treatments, e.g. food, rest, herbal remedies, instead of bloodletting and purging.