calculating a difference between the known volume of the cavity and the measured volume of discharged fluid into {TAIL ~ the cavity} to determine {HEAD ~ the volume} of the persons body 
calculating a difference between the known volume of the cavity and the measured volume of discharged fluid into { TAIL ~ the cavity } to determine { HEAD ~ the volume } of the persons body
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH