At 21st day, the cell number in posterior horn decreased, glial cell proliferated and demyelination occurred characterized by brisement and fragmentation of lamellar texture of myelin sheath even with axis cylinder destruction. 第21天出现前角细胞数量减少,胶质细胞增生,髓鞘板层状结构断裂,呈脱髓鞘改变,甚至轴索破坏。