This substance was mentioned for the first time in the SHEN NONG BEN CAO JING.
It is produced in the provinces of GUANG XI, GUANG DONG and YUN NAN, and is harvested in Spring and Summer.
The parts of the plant which are used are the tender stems a

Class: Release the Exterior
Subclass: Pungent and Warm Formulas
Name:
Pinyin: Gui Zhi
Pharmaceutical: Ramulus Cinnamomi Cassiae
Other names: Chuan Gui Zhi
Description: Cinnamon Twig.
Properties:
Nature: Warm.
Taste: Pungent, sweet.
Organ: Heart, Lungs, Bladder.
Toxicity: Non toxic.
Actions:
Promotes sweating.
Releases the Exterior.
Warms the channels.
Tonifies the Yang.
Comparisons:
Ma Huang is very effective to promote sweating.
Warning:
Contraindications: Yin Deficiency, Yang rising.
Vere severe Yin Deficiency.
Warm-febrile disease.
Throat disorders.
Menorrhagia.
Pregnancy.