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