Every such banking corporation may accept drafts or bills of exchange drawn upon it having not more than six months’ sight to run, exclusive of grace, which (a) grow out of transactions involving the importation or exportation of goods or the domestic shipment of goods, provided shipping documents conveying or securing title are attached at the time of acceptance, or (b) are secured at the time of acceptance by a warehouse receipt or other such document conveying or securing title covering readily marketable staples. No such banking corporation shall accept, whether in a foreign or domestic transaction, for any one person an amount equal at any one time in the aggregate to more than ten per cent of its paid-up and unimpaired capital stock and surplus, unless the banking corporation is secured either by attached documents or by some other actual security arising out of the same transaction as the acceptance. And no banking corporation shall accept such bills to an amount equal at any time in the aggregate to more than one half of its paid-up and unimpaired capital stock and surplus. But the Commissioner of Banking, under such general regulations as he may prescribe which shall apply to all banking corporations alike regardless of the amount of capital stock and surplus, may authorize any banking corporation to accept such bills to an amount not exceeding at any time in the aggregate one hundred per cent of its paid-up and unimpaired capital stock and surplus.