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