{HEAD ~ The guinea pigs} are housed under {TAIL ~ standard laboratory conditions} on a 7 a.m. to 7 p.m. lighting schedule for at least seven days prior to experimentation 
are housed under
{ HEAD ~ The guinea pigs } are housed under { TAIL ~ standard laboratory conditions } on a 7 a.m. to 7 p.m. lighting schedule for at least seven days prior to experimentation
HEAD HEAD HEAD HEAD HEAD HEAD HEAD 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