140 HEAD AND NECK 



passed through the puncta into the lacrimal ducts and along 

 the ducts into the lacrimal sac (Fig. 64). 



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 passed down the naso- lacrimal duct into the 

 nose. Note that as the probe passes along the duct it 

 inclines downwards, laterally and slightly posteriorly. 



Pars Lacrimalis Orbicularis Oculi (O.T. Tensor Tarsi}. 

 This small special portion of the orbicularis oculi springs 

 from the posterior aspect of the lateral part of the medial 

 palpebral ligament and passes posteriorly 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 contracts 

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

 flow of the lacrimal secretion into the nose. 



Ductus Naso -Lacrimalis. This duct will be seen at a 

 later period of the dissection. It is a bony canal, lined with 

 muco-periosteum, which runs, in the lateral wall of the nose, 

 from the lacrimal sac to the upper and anterior part of the 

 inferior meatus. It is about half an inch long. At the medial 

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

 lacrimalis, which serves as a flap valve (Fig. 64). 



The dissection of the face should be completed by an 

 examination of the nasal cartilages and the external nasal 

 branch of the ophthalmic division of the trigeminal nerve. 

 The nerve will be found emerging between the lower border 

 of the nasal bone and the lateral cartilage. After its 

 emergence it descends to the tip of the nose supplying 

 filaments to the skin. 



Dissection. The cartilaginous part of the nose should now be examined 

 by stripping off the nasalis muscle and the remains of the integument. 



Nasal Cartilages. In addition to the septal cartilage, 



