怎么理解这里的what ,是从句还是副词he went off immediately to visit him, carrying with him in his pocket 【what remained of a bottle of medicine】 formerly prescribed for an indisposition of Mrs. Carlyle's.分析一下语法这是什么用法,怎样翻译

问题描述:

怎么理解这里的what ,是从句还是副词
he went off immediately to visit him, carrying with him in his pocket 【what remained of a bottle of medicine】 formerly prescribed for an indisposition of Mrs. Carlyle's.
分析一下语法
这是什么用法,怎样翻译