function doSend(
        address _operator,
        address _from,
        address _to,
        uint256 _amount,
        bytes _userData,
        bytes _operatorData,
        bool _preventLocking
    )
        internal
    {
        requireMultiple(_amount);

        callSender(_operator, _from, _to, _amount, _userData, _operatorData);

        require(_to != address(0));          
        require(mBalances[_from] >= _amount); 

        mBalances[_from] = mBalances[_from].sub(_amount);
        mBalances[_to] = mBalances[_to].add(_amount);

        callRecipient(_operator, _from, _to, _amount, _userData, _operatorData, _preventLocking);

        emit Sent(_operator, _from, _to, _amount, _userData, _operatorData);
    }