Representation by sub-agent creates principal liability for the sub-agent's acts; agent remains liable to principal and sub-agent to agent. A properly appointed sub-agent represents the principal to third persons and the principal is bound by the sub-agent's acts as if originally appointed by the principal; the agent is responsible to the principal for the sub-agent's acts, while the sub-agent is responsible to the agent and not to the principal except in cases of fraud or wilful wrong.