316 PROCEEDINGS OF THE CANADIAN INSTITUTE, 
Tnnervation.—A branch from an anastomosis of &. mawillaris inf. 
trigemini and R. hyoideo-mandibularis facialis. 
Action.—Prevents the separation of the ramiof the mandibles 
whether from pressure within or from the action of the lev. arcés 
palatens. 
II1.— MUSCLES OF THE PALATINE ARCH. 
1. Levator Arcits Paratini, (No. 24, Cuv.; Lev. suspensoru, Stan.; 
Lev. tympani, Ow.) (Figs. 1 & 2, LAP). 
This is exposed on cutting through the upper and posterior 
portions of the insertion of the add. mand., and reflecting it. 
The muscle may be described as consisting of two parts. The 
anterior portion is triangular and thick, and arises from the poste- 
rior border of the antorbital process and from the inferior surface 
and the edge of the ectethmoid and frontal. Its fibres arching 
over the orbit and passing below the add. mand., unite to a tendon, 
which is inserted into the extremity of the transverse ridge of the 
hyomandibular. The postercor part is quadrangular and thin, and 
arises from the edge of the sphenotic. Those fibres arising from the 
rudimentary postorbital process are at first tendinous but soon be- 
come muscular, and, along with the more anterior ones, pass directly 
downwards to be inserted along the whole upper surface of the trans- 
verse ridge on the hyomandibular, a few fibres passing to the surface 
of the bone above the ridge. 
Innervation.—It is supplied by a branch from an independent 
strand of the trigeminus which accompanies the k. maaillaris sup. 
Action.—It raises the palatine arch. The anterior triangular por- 
tion will also pull it forwards. 
This muscle is very similar in its relations to that of Hsoz, but dif- 
fers slightly from that of other forms. The innervation differs also 
slightly, Vetter describing it in the forms he studied as being by a 
branch from the R. maxillaris inferior. Here, however, the inde- 
pendent strand must be equivalent to this branch, since like it it 
also supplies the dilatator operculi. The great differentiation which 
the trigeminus shows accounts for these slight dissimilarities. 
9. Appuctor Arctis Patatini, (No. 22, Cuv. ; Constrictor, Stan. ; 
Depressor tympani, Ow.) 
This consists of two distinct parrs. The posterior portion is ex- 
posed by removing the branchial and lower part of the hyoid appara- 
