Replicate the rat model by methods of phlorus spring insertion and hot paste, observe effects of Sanqi (Notoginseng) and tretinoin on the morphologic change of gastric mucosa.

• 采用幽门弹簧插入加热糊复合方法复制大鼠慢性萎缩性胃炎癌前病变模型，观察三七和维甲酸对胃粘膜形态学改变的影响。