FACE AND FRONTAL REGION OF HEAD 29 



The Conjunctival Sac. The cavity of the conjunctiva! 

 sac is the potential space between the eyelids and the eyeball. 

 It opens externally through the rima, and communicates with 

 the lacrimal sac through the puncta and the lacrimal ducts. 



Puncta Lacrimalia. It has been noted already that the 

 punctum lacrimale of each lid lies at the lateral margin of 

 the lacus lacrimalis (p. 4). Small probes should now be 

 passed through the puncta into the lacrimal ducts and along 

 the ducts into the lacrimal sac (Fig. 9). 



Saccus Lacrimalis. The lacrimal sac is the blind upper 

 end of a canal which extends from the orbit to the inferior 

 meatus of the nose. It is lodged in the fossa lacrimalis in 

 the anterior part of the medial wall of the orbit. It lies 

 posterior to the medial palpebral ligament, from which it 

 receives a fibrous expansion, and it is covered on its lateral 

 aspect, and on the lateral part of its posterior aspect, by 

 the pars lacrimalis of the orbicularis oculi. The lacrimal 

 ducts open into its antero- lateral aspect, under cover of 

 the medial palpebral ligament; and it is continuous below 

 with the naso-lacrimal duct. The anterior wall of the sac 

 should be incised and a probe should be passed down the 

 naso-lacrimal duct into the inferior meatus of the nose. Note 

 that as the probe passes along the duct it inclines down- 

 wards, laterally and slightly backwards. 



Pars Lacrimalis M. Orbicularis Oculi (O.T. Tensor 

 Tarsi], The lacrimal part of the orbicularis oculi springs 

 from the posterior aspect of the lateral part of the medial 

 palpebral ligament and passes backwards and medially, round 

 the lateral part of the lacrimal sac, to the crista lacrimalis 

 of the lacrimal bone, to which it is attached. When it con- 

 tracts it compresses the lacrimal sac, and so tends to facilitate 

 the flow of the lacrimal secretion into the nose. 



Ductus Naso-Lacrimalis. The naso-lacrimal duct will be 

 seen at a later period of the dissection. It lies in a bony 

 canal in the lateral wall of the nose, and extends from the 

 lacrimal sac to the upper and anterior part of the inferior 

 meatus. It is about 12.5 mm. (half an inch) long, and its 

 walls are composed of muco-periosteum. At the medial side 

 of its lower end is a fold of mucous membrane, the plica 

 lacrimalis, which serves as a flap valve (Fig. 9). 



Dissection. The dissection of the face should be completed 

 by an examination of the nasal cartilages and the external nasal 



