{HEAD ~ The base} is perforated by {TAIL ~ at least one port} whose length is very much less than the mean diameter and the base, external to the box is capped by a flexible and sealed bellows adapted to form with it a pocket of variable volume 
is perforated by
{ HEAD ~ The base } is perforated by { TAIL ~ at least one port } whose length is very much less than the mean diameter and the base , external to the box is capped by a flexible and sealed bellows adapted to form with it a pocket of variable volume
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH