material which supports a coil like electrode 4 and a rear fin like electrode 6 wires 8 and 10 are connected to respective electrodes 4 and 6 and pass through a flexible driver tube 12 having slots 13 which releaseably engage the fin like electrode 6 driver tube 12 can thus be used to push the electrode structure through the vaginal canal and turn it to engage the sharp coil like electrode 4 within the tissue of a fetus contained therein a curved guide tube 14 is provided to assist in passing the electrode structure and driver tube 12 through the vaginal canal and to prevent the electrode 4 from snagging intermediate body tissue before it has reached the intended point of engagement the construction purpose and method of this probe is explained in greater detail in u s pat no 3 827 428 after the electrode 4 is secured the guide tube 14 and driver tube 12 are removed leaving the electrode structure in place within the body with the ends of wires 8 and 10 opposite those attached to electrodes 4 and 6 extending from the cervix for attachment to external electrical apparatus e g a fetal heart monitor in order to maintain the rear electrode 6 within the slots 13 of driver tube 12 so that the electrode structure may be pushed through a body orifice and turned the wires 8 and 10 are held in tension so that the holder 2 abuts against the forward end of driver tube 12 this is achieved by clamping wires 8 and 10 which are firmly secured within the holder 2 to the rear end of driver tube 12.