A piston is disposed in each cylinder for reciprocal movement therein in order to pump {HEAD ~ the fluuid} from the inlet to {TAIL ~ the outlet} 
to
A piston is disposed in each cylinder for reciprocal movement therein in order to pump { HEAD ~ the fluuid } from the inlet to { TAIL ~ the outlet }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL