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TEMPORALIS.
20 — —
This Muscle arises from all the bones of the side of the
Head, that are within the line, for insertion of the tendinous
Fascia, viz., from the lower and lateral part of the Parietal
Bone, from all the squammous portion of the Temporal Bone,
from the lower and lateral part of the Os Frontis, from all the
Temporal Process of the Os Sphenoides, and often from a pro-
cess at the lower part of this surface, (which portion, however,
is often common to this Muscle, and the Pterygoidseus externus)

condyle and glenoid cavity are specially adapted. In the Rodents, the
lower border of the zygoma is convex, the curve of the vertical arch
being always in the opposite direction to that which is constant in the
Carnivora ; in some species e. g., the capybara, the agoutis, and pacas
—the convexity of the arch descends to a level below that of the superior
grinders. The superior maxillary bone contributes also to its formation,
the malar being frequently, as it were, suspended between its
apophysis and the zygomatic process of the temporal bone. In these
animals the masseter is of great strength when compared with the
temporal, and it is divided into several distinct portions, which in
some species may rank as separate muscles. A large portion of
the muscle will be found to arise from the superior maxillary and
fore part of the arch, and to pass obliquely backwards, its action
being to bring the jaw directly forwards. In many instances a muscular
fasciculus commences by a strong tendon under the sub-orbital foramen,
and passes nearly directly backwards ; in the agouti this portion of the
masseter covers the posterior half of the jaw, and terminates on the
internal surface of its posterior border. Other fibres have a more per-
pendicular arrangement, and in some species e.g., the rabbits—the
fibres of a small portion of the muscle will be found to run in the oppo-
site direction to the larger mass. They assist in moving the jaw
upwards and backwards. (1)
In Man and the Quadrumana, the zygomatic bar is nearly transverse.
In the latter it is of greater length, in conformity with the relative di-
mensions of the cranium and face it is also somewhat more curved, the
;
upper border being slightly convex behind and concave in front.
In the larger Anthropoid Apes (TV. Gorilla and Pith. Satyrus) the
massive dimensions of the zygoma, dependant on the great size of the
lower jaw and the development of the canine teeth, present a striking
contrast with the human configuration. (2)]
(1) Vide Cuvier, Logons d' Anatomic Comparcc, T. iv., partie 1, lecon xvi.,
edit. 1835.
Vide Owen, Zool. Trans.
(2)