Where a sub-agent is properly appointed, the principal is, so far as regards third persons, represented by the sub-agent, and is bound by and responsible for his acts, as if he were an agent originally appointed by the principal.
     Agent's responsibility for sub-agent.—The agent is responsible to the principal for the acts of the sub-agent.
     Sub-agent's responsibility.—The sub-agent is responsible for his acts to the agent, but not to the principal, except in cases of fraud or wilful wrong.