230 THE MUSCLES. 



extensive. In all the animals, the stylo-maxillaris fasciculus of the digastricus ia 

 entirely absent, and the muscle has only a single belly extending directly from the 

 occipital to the maxillary bone. In the Ox is found a small square muscle, formed of 

 transverse fibres, which unites the two digastric muscles by passing beneath the base of 

 the tongue. This muscle, in contracting, may raise the hyoideal apparatus, and in this 

 way supplements the tendon of the digastricus and the inferior ring of the stylo- 

 hyoideus. 



C. Hyoid Region, 



The two fleshy planes composing the mylo-hyoideus are more distinct in Buminants 

 than in the Horse. The stylo-hyoideus of these animals commences by a long thin 

 tendon. The muscle has no ring for the passage of the digastricus, a feature observed 

 in all the domesticated animals except Solipeds. 



In the Carnivora, the ntylo-hyoideus, formed by a narrow, very thin, and pale 

 fleshy band, commences on the mastoid portion of the temporal bone by a small tendon; 

 the kerato-hyoideus is remarkable for its relatively considerable volume ; the ocaipito- 

 slyloideus and tlie tramversalis hyoideus aie absent. 



COMPAKIS0>f OF THE MUSCLES OP THE HUMAN HEAD WITH THOSE OF THE DOMESTICATED 



ANIMALS. 



In Man, there are described as muscles of the head, the epicranial muscles, muscles of 

 the face, and those o( the lotuer jaw. The hyoid and digastric muscles are reckoned in 

 the region of the neck. Here they will be placed in the region of the head. 



A. Epicranial Muscles. 



The middle portion of the human cranium is covered by an aponeurosis that adheres 

 closely to the hairy scalp, but glides easily on the surface of the bones. To the circum- 

 ference of this epicranial aponeurosis are attached four muscles which move it. One 

 of them, attached behind to the superior occipital curved line, is named the occipital 

 muscle ; another, fixed in front of the forehead, is called the frontal muscle ; the other two, 

 double and lateral, are inserted on the face of the temporal bone or the external ear, 

 and are designated auricular muscles. These epicranial muscles move the scalp for- 

 wards, backwards, and sideways. 



B. Muscles of the Face. 



These are fourteen in number, ten of which are found in the domesticated animals. 

 We commence by describing these common muscles (fig. 113). 



1. The orbicularis of the lips, which has a fasciculus that passes to the skin from the 

 columna of the nose ; this fasciculus is termed the depressor of the columna, or 

 moustache muscle (naso lahialis). 



2. The buccinator, corresponding to the alveolo-labialis of animals. Besides its office 

 in mastication, it takes an important part in the blowing of wind instruments. 



3. The superficial elevator of the wing of the nose and the upper lip. It resembles the 

 supernaso-labialis, descends from the orbital margin of the supermaxilla, passes along 

 the wing of the nose, and is lost In the upper lip. 



4. The deep elevator of the wing of the nose and the upper lip, whose analogue is 

 found in the supermaxillo-labialis of animals. 



5. The great zygomaticus, whose presence is constant in all species. 



6. The small zygomaticus. represented in the Horse by only the small oblique 

 fasciculus sometimes found beneath the great zygomaticus. 



The small zygomaticus and the two elevators of the lips are lachrymal muscles ; by 

 their simultaneous contraction they express discimtent and melanclioly. The great 

 zygomaticus, on the contrary, is the muscle of laughter ; it draws the commissures of 

 the lips outwards. 



7. The canine, or great supennaxillo-nasal of animals, is attached beneath the infra- 

 orbital foramen, and terminates in the skin of the upper lip. 



8. The risorius of Santortni. 



9. The muscle of the chin (mento-lahialis). 



10. The myrtiformis, or middle anterior of Eourgelat. 



The ether facial muscles of Man, whose analogues it is difficult or impossible to find 

 in animals, are : — 



