The apparatus comprises a first chamber, a second chamber connected to the first chamber, and {HEAD ~ a third chamber} connected to {TAIL ~ the second chamber} 
connected to
The apparatus comprises a first chamber , a second chamber connected to the first chamber , and { HEAD ~ a third chamber } connected to { TAIL ~ the second chamber }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL