They're not trading in securities, although they would deal in securities as a part of the underwriting process.

他们不买卖证券，虽然在经营证券,是他们承销的一个环节。

耶鲁公开课 - 金融市场课程节选

It's one of the most rapidly changing, hard to keep up with areas because someone can set up an electronic exchange overnight and suddenly become a base for trading trillions of dollars of securities.

经纪业是一个变化最快的行业之一,人们很难跟上它的步伐,因为人们可以在头一天晚上,设置一个电子交易,一夜之间,他就能在证券市场赚到千亿美金

耶鲁公开课 - 金融市场课程节选