Comb 27 may be flat, or it may form, as in FIG 10, {HEAD ~ a channel} leading towards {TAIL ~ guide} 13, and the channel may decrease in cross section towards guide 13 
leading towards
Comb 27 may be flat , or it may form , as in FIG 10 , { HEAD ~ a channel } leading towards { TAIL ~ guide } 13 , and the channel may decrease in cross section towards guide 13
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH