At the base of the feather, the rachis expands to form the hollow tubular calamus, or quill, which inserts into a follicle in the skin.是什么意思_At the base of the feather, the rachis expands to form the hollow tubular calamus, or quill, which inserts into a follicle in the skin.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句