Certain masses oscillating about the z axis are tiltable about the x axis, while {TAIL ~ some others} are tiltable about {HEAD ~ the y axis} 
Certain masses oscillating about the z axis are tiltable about the x axis , while { TAIL ~ some others } are tiltable about { HEAD ~ the y axis }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD