In any action brought in his own name by the assignee of a chose in action not negotiable, the defendant, or any of the defendants, may set off, in the manner and to the extent provided in section 52-139, any mutual debt between him and the plaintiff or any of the plaintiffs, or between him and the assignors of such chose in action, or any of them.
Conn. Gen. Stat. § 52-140
(1949 Rev., S. 7861.)