Abstract: A dual cannula having two adjoining tubes, a leader tube and a follower tube, in staggered arrangement so as to form two separate and distinct passageways for the withdrawal and return of blood to a body. The blood return passageway terminates with a needle aperture and the blood withdrawal passageway has a sheltered aperture. The outer dimensions of the needle portion of the leader tube are substantially the same as the total outer dimensions of the two adjoining tubes for the distance which the cannula is adapted to be inserted into a body, whereby the sheltered aperture is sheltered by the needle portion of the leader tube. Means are provided for shielding the sheltered aperture.