262 SPECIAL ANATOMY. 



pendently, in the anterior external part of the lacrymal sac, behind lig. pal- 

 pebrale internum. The commencement is somewhat wider than the remain- 

 ing part, in the whole a capillary tubule ; the walls thick and elastic, covered 

 before by fibres of TO. orbicularis, behind by fibres of m. Horneri, consist of 

 mucous membrane. 



Muse. Horneri [tensor tarsi] arises from the crista lacrymalis, passes 

 transversely outwards, is divided by lig. palpebr. intern., and attaches 

 itself to the internal angle of the eye, drawing the lids inwards, and 

 making the puncta deeper in the lacus lacrymalis, where they take up 

 the lacrymal moisture and carry it into 



c. The lacrymal sac and duct. These two form one canal (canalis lacry- 

 malis oss. unguis), which extends from the eye as far as the nose ; secretes a 

 mucous fluid, and carries this, together with the tears, into the nose. The 

 lacrymal sac, saccus lacrymal., an oblong but closed sac, formed of soft, red- 

 dish mucous membrane, united by areolar tissue on the inner side with the 

 fossa lacrymal. (os unguis andproc. nasalis of the upper jaw) on the external 

 with a fibrous continuation of m. orbicularis ; it lies, close behind the internal 

 inferior angle of basis orbitce, behind and under the lig. palpebrale intern., 

 above which the caecal extremity of the sac, only, projects a little upwards. 

 On the external surface is placed m. Horneri. The lacrymal canaliculi open 

 close behind lig. palpebr. Below it continues into the 



Lacrymal duct, ductus (naso-) lacrymalis a membranous canal flattened on 

 the sides, somewhat contracted in the centre, which, slightly curved forwards 

 and outwards, descends in the osseous canalis lacrymalis to the nasal cavity, 

 and opens into the inferior nasal chamber below the anterior part of the 

 inferior turbinate bone (sometimes in a fold of mucous membrane which 

 elongates the ducts a few lines). Internally it lies on the meatus narium and 

 concha inferior; externally on the thin wall of the antrum Highmori. 

 Arter. : branches of opkthalmica. Nerves: infra- and supra-trochlearis 

 (nerv. ophthalmici). 



495. 5. The muscles of the eyes. 



These are placed together inside the orbits, in the depth of 

 which they arise and form a circle around the IV. oplicus and the 

 nerves of motion. 



a. M. lev. palpeb. superioris (see Myologia). 



b. Mm. recti bulbi oculi, the four straight muscles of the eye. 



Origins: round about the foramen opticum. Insertions: with a broader 

 aponeurosis to the Sclerotica, convex towards the Cornea and in its proximity. 

 Position : one surface turned towards the walls of the orbit, the other towards 

 the optic nerve and the globe of the eye ; separated from these by adipose 

 tissue and vessels ; in a straight direction from behind forwards, curved on 

 the globe. The opening in the capsule for rect. intern, is rather higher than 

 the internal, for rect. extern, on the same plane with the external angle of the 



