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