a plurality of {HEAD ~ spaced spherical interrupter elements} extending along {TAIL ~ the said core element}, the core element being free of interrupter elements at its ends 
extending along
a plurality of { HEAD ~ spaced spherical interrupter elements } extending along { TAIL ~ the said core element } , the core element being free of interrupter elements at its ends
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH