Initiation may be achieved by adding a blood coagulation factor XII activator to animal plasma in {HEAD ~ the presence} of {TAIL ~ the test substance} 
of
Initiation may be achieved by adding a blood coagulation factor XII activator to animal plasma in { HEAD ~ the presence } of { TAIL ~ the test substance }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL