Intervention is an act whereby a person becomes a party to a negotiable instrument, whether by accepting the bill or by paying the sum indicated thereon, in order to relieve one of the obligors on the bill from the action of recourse that the holder could assert against him in consequence of default of acceptance or payment by the drawee.

The complexity of the material to be discussed renders it necessary, in order to clarify the development of the exposition, for us to advance several concepts, which will later be considered more fully at the proper places.