368 



THE MUSCLES AND FASCIA 



outer angle of the eyelids, which give rise in old age to the so-called "crow's feet." The Levator 

 palpebrae is the direct antagonist of this muscle; it raises the upper eyelid and exposes the globe 

 of the eye. The Corrugator supercilii draws the eyebrow downward and inward, producing the 

 vertical wrinkles of the forehead. It is the "frowning" muscle, and may be regarded as the 

 principal agent in the expression of suffering. The Tensor tarsi draws the eyelids inward and 

 compresses the eyelids and the extremities of the lacrimal canals against the surface of the globe 

 of the eye; thus placing the canals in the most favorable situation for receiving the tears. It 

 serves, also, to compress the lacrimal sac. 



FRONTAL SINUS 



PALPCBRAL PORTION 



OF ORBICULARIS 



PALPEBRARUM 



LACRIMALIA 



ORBITAL PORTION OF 

 ORBICULARIS PALPEBRARUM 



ANTRUM OF 

 HIGHMORE 



FIG. 290. The three portions of the Orbicularis palpebrarum muscle, and the relation of this muscle to the 

 Corrugator supercilii muscle, seen from behind. (Left side.) (Toldt.) 



4. The Orbital Region (Fig. 292). 



Levator palpebrae superioris. Rectus interims. 



Rectus superior. Rectus externus. 



Rectus inferior. Obliquus oculi superior. 



Obliquus oculi inferior. 



Dissection. To open the cavity of the orbit, remove the skullcap and brain ; then saw through 

 the frontal bone at the inner extremity of the supraorbital ridge, and externally at its junction 

 with the malar. Break in pieces the thin roof of the orbit by a few slight blows of the hammer, 

 and take it away; drive forward the superciliary portion of the frontal bone by a smart stroke, 

 but do not remove it, as that would destroy the pulley of the Obliquus superior. When the 

 fragments are cleared away, the periosteum of the orbit will be exposed; this being removed, 

 together with the fat which fills the cavity of the orbit, the several muscles of this region can 

 be examined. The dissection will be facilitated by distending the globe of the eye. In order 

 to effect this, puncture the optic nerve near the eyeball with a curved needle, and push the needle 

 onward into the globe; insert the point of a blowpipe through this aperture, and force a little 

 air into the cavity of the eyeball; then apply a ligature around the nerve so as to prevent the air 

 escaping. The globe being now drawn forward, the muscles will be put upon the stretch. 



Orbital Septum. Subjacent to the Orbicularis palpebrarum a dense fascia! 

 sheet supports the tarsal plates and serves as a septum (septum orbitale], which 

 is attached to the orbital margin. It is perforated by the small vessels and 



