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