feather sac

• 毛囊

feather sac的用法和样例：

例句

1. Proliferation of cells in a ring around the feather germ creates a cylindrical depression, the follicle, at its base.
   环绕羽芽有一圈细胞不断增生，在基部形成圆柱状凹陷，称为毛囊。