As a rule, banks do not make known even to a single individual the extent of a customer's business or the size of his bank account. However, any shareholder in a bank has a right, as one of the proprietors, to examine the books, so long as such examination is not an unreasonable interference with the regular routine of work, and it is pretty generally known that a large depositor can either directly or through some other bank get at the condition of a small depositor's account.