allowing {HEAD ~ the second reagent} to be absorbed through {TAIL ~ the top layer} of the pad to activate the first reagent by flowing through the rupturable seal after breaking to form an activated chemical test pad in the sealed package 
to be absorbed through
allowing { HEAD ~ the second reagent } to be absorbed through { TAIL ~ the top layer } of the pad to activate the first reagent by flowing through the rupturable seal after breaking to form an activated chemical test pad in the sealed package
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL 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