The =panniculus= is much more developed than in the horse, presenting as
a special feature the extensive =frontalis= muscle, which covers the
frontal and nasal regions.
The =orbicularis oris= does not form a complete ring, the defect being
in the middle of the upper lip.
The =levator nasolabialis= is extensive, thin, and not very distinct
from the frontalis; it divides into two layers, between which the
levator labii superioris proprius and the lateral dilator of the nostril
pass. The superficial layer ends in the nostril and upper lip, the deep
layer on the accessory (lateral) nasal cartilages and on the nasal
process of the premaxilla.
The =levator labii superioris proprius= arises on and before the facial
tuberosity and terminates by several tendons in the muzzle. It passes
between the two layers of the preceding muscle, blending in part with
the deep layer.
The =zygomaticus= is much stronger than in the horse. It arises on the
masseteric fascia, and ends chiefly in the upper lip.
The =depressor labii superioris= does not resemble the muscle of the
same name in the horse. It arises just in front of the facial
tuberosity, and divides usually into two branches, which terminate in a
number of tendons that form a network in the muzzle and upper lip.
The =incisivus inferior= is a small, rounded muscle, which arises on the
body of the mandible below the second and third incisors, and ends in
the lower lip, blending with the orbicularis.
The =depressor labii inferioris= is thin, and does not extend as far
backward as in the horse; only the anterior end is distinct from the
buccinator.
The =buccinator= shows no marked variation, but its superficial layer is
well developed.
The =dilatator naris lateralis= arises in front of the facial
tuberosity, passes forward between the branches of the levator
nasolabialis, and terminates in the outer wing of the nostril.
The dilatator naris transversus is replaced by the =dilatator naris
apicalis=, which is situated in the muzzle and joins its fellow at a
median raphé. It arises on the border and upper surface of the body of
the premaxilla, the fibers passing obliquely upward and outward to the
inner wing of the nostril.
The =dilatator naris superior= arises from the alar cartilage of the
nostril and ends in the inner wing of the nostril.
[Illustration: