介词及what

He was depressed by what he had gone through.

He was depressed by what he had known.

1. 我看到曹老师解答的时候提到what在这种结构中引导的是名词性从句，但没说是什么种类的名词性从句，请问老师是什么种类的名词性从句呢？之前有老师把第一句剖析为“宾语从句”，这种说法对吗？

2. by的词性是介词吗？bywhat he had known作什么成分呢？

1. 问题句的这种结构可以称为名词性结构，等于the thing that...不当作从句理解。

2. 问题句为被动语态，by 当然是介词,by 引导的部分作方法状语。《薄冰高级英语语法》是如此讲解的。