302 



THE MUSCLES AND FASCIA. 



HORNER'S MUSCLE. 



ORD1CULARIS 

 PALPEBRARUM. 



fascia. On the eyelids it is separated from the conjunctiva by the Levator palpe- 

 brse, the tarsal ligaments, the tarsal plates, and the Meibomian glands. 



The tendo oculi (internal tarsal ligament) is a short tendon, about two lines in 

 length and one in breadth, attached to the nasal process of the superior maxillary 

 bone in front of the lachrymal groove. Crossing the lachrymal sac, it divides into 

 two parts, each division being attached to the inner extremity of the corresponding 

 tarsal plate. As the tendon crosses the lachrymal sac, a strong aponeurotic lamina is 

 given off from the posterior surface', which expands over the sac, and is attached to the 

 ridge on the lachrymal bone. This is the reflected aponeurosis of the tendo oculi. 

 The external tarsal ligament is a much weaker structure than the tendo oculi. 

 It is attached to the margin of the frontal process of the malar bone, and passes 

 inward to the outer commissure of the eyelids ; it connects together the outer 

 extremities of the two tarsal cartilages. 



Use of Tendo oculi. Besides giving attachment to part of the Orbicularis palpe- 

 brarum and to the tarsal plates, it serves to suck the tears into the lachrymal sac, 

 by its attachment to the sac. Thus, each time the eyelids are closed, the tendo 

 oculi becomes tightened, through the action of the Orbicularis, and draws the wall 

 of the lachrymal sac outward and forward, so that a vacuum is made in the sac, and 

 the tears are sucked along the lachrymal canals into it. 



The Corrugator supercilii is a small, narrow, pyramidal muscle, placed at the 

 inner extremity of the eyebrow, beneath the Occipito-frontalis and Orbicularis 



palpebrarum muscles. It arises from 

 the inner extremity of the supercil- 

 iary ridge, from whence its fibres 

 pass upward and outward, and, pass- 

 ing between the palpebral and orbital 

 portions of the Orbicularis palpebra- 

 rum, are inserted into the deep surface 

 of the skin, opposite the middle of 

 the orbital arch. 



Relations. By its anterior sur- 

 face with the Occipito-frontalis and 

 Orbicularis palpebrarum muscles ; 

 by its posterior surface, with the 

 frontal bone and supratrochlear 

 nerve. 



The Levator palpebrae will be 

 described with the muscles of the 

 orbital region. 



The Tensor tarsi (Homer's 

 muscle) (Fig. 196) is a small thin 

 muscle about three lines in breadth 

 and six in length, situated at the 

 inner side of the orbit, behind the 

 tendo oculi. It arises from the crest 

 and adjacent part of the orbital sur- 

 face of the lachrymal bone, and, 

 passing across the lachrymal sac, divides into two slips, which cover the lachrymal 

 canals and are inserted into the tarsal plates internal to the puncta lachrymalia. 

 Its fibres appear to be continuous with those of the palpebral portion of the 

 Orbicularis palpebrarum ; it is occasionally very indistinct. 



Nerves. The Orbicularis palpebrarum, Corrugator supercilii, and Tensor tarsi 

 are supplied by the facial nerve. Recent investigations tend to show that the 

 Orbicularis palpebrarum, Corrugator supercilii, and frontal part of the Occipito- 

 frontalis are in reality supplied by fibres of the third nerve, which descend through 

 the pons varolii to join the facial nerve. 



Actions. The Orbicularis palpebrarum is the sphincter muscle of the eyelids. 



ORBICULA- 

 RIS PALPE- 

 BRARUM. 



LEV. LAB. 

 SUP. AL>C- 

 QUE NASI. 



FIG. 196. Homer's muscle. (From a preparation in the 

 Museum of the Royal College of Surgeons of England.) 



