The slider includes: a first cylindrical portion having an upstream through hole penetrating therethrough; a second cylindrical portion having a downstream through hole penetrating therethrough and communicating with the upstream through hole; and {HEAD ~ a semipermeable membrane} closing {TAIL ~ the upstream} through hole 
The slider includes : a first cylindrical portion having an upstream through hole penetrating therethrough ; a second cylindrical portion having a downstream through hole penetrating therethrough and communicating with the upstream through hole ; and { HEAD ~ a semipermeable membrane } closing { TAIL ~ the upstream } through hole
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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH