386 THE HORSE. 
the various groups of muscles. Externally it is inserted at short intervals 
into the inner surface of the skin, and into the cellular membrane beneath 
it. Its action is to throw the skin ,into folds or wrinkles, in so sudden a 
manner as to dislodge flies or other irritating insects. It is also powerful 
enough to shake off particles of dust ov dirt which have fallen upon the 
part, and are not glued to it by any adhesive matter. 
MUSCLES OF THE HEAD. 
THE MUSCLES OF THE HEAD are in number above sixty, chiefly arranged 
in pairs, which correspond exactly with each other. Want of space will 
not permit a minute description of each ; but the most important will 
be found alluded to sufficiently to give an idea of their position and 
action :— 
Fig. 1.—SUPERFICIAL MUSCLES OF THE HEAD, 
1. Masseter. 9. Dilatator naris anterior. 
2. Nasalis longns labii superioris. 10, 10. Orbicularis oris. 
3, 4. Levator labii superioris aleeque nasi. ll. a. a. Orbicularis palpebrarum. 
5, Dilatator naris lateralis. — |b. Levator palpebre superioris, or corrn- 
6. Zygomaticus. gator svpercilil. 
7. Retractor labii inferioris. 12. Parotido auricularis. 
8. Depressor labii inferioris. 13. Splenius. 
ANTERIOR MAXILLARY REGION. 
ZYGOMATICUS. —Situation on the middle of the side of the face. 
Origin—trom the anterior two-thirds of the zygomatic ridge. Insertion 
—to the angle of the mouth. Actton—to retract the angle of the mouth. 
LEVATOR LABIL SUPERIORIS ALZQUE NASI is situated on and above the 
side of the face. Ovrigin—from the lachrymal, malar, and superior 
maxillary bones. Jnsertion—to the supero-posterior part of the nasal 
opening, and to the antero-inferior part of the nostril and upper lip. 
Action—to dilate the nostrils and to retract the upper lip. 
RETRACTOR LABIL SUPERIORIS is situated on the side of the face. 
Origin—from the anterior part of the zygomatic ridge, and from the 
corresponding part of the superior maxillary bone. Jnserteon—to the 
sides of the nostril and supero-lateral parts of the upper ip. <Action—to 
retract the upper lip. 
NASALIS LONGUS LABII SUPERIORIS is situated on the upper part of the 
face. Origin—from the infero-external part of the lachrymal and malar 
