THE EYE 



209 



lacrinial duct. This duct lies in a bony canal in the lateral 

 wall of the nose and opens below into the forepart of the 

 inferior meatus of the nose, under cover of the anterior 

 extremity of the inferior concha (turbinated bone). It is only 

 half an inch long and is provided, near its lower end, with a 

 small valve, which prevents the upward passage of air or fluids 

 from the nose to the lacrimal sac. 



The secreto-motor 



nerves 



of the lacrimal gland are derived 



FIG. 81. The Lacrimal Apparatus. (TURNER'S Anatomy.} 



i. Orbicularis oculi muscle. 

 2, 3. Lacrimal canals. 

 4. Lacrimal caruncle. 



5. Lacrimal sac. 



6. Naso-lacrimal duct. 



7. Angular artery. 



from the lacrimal branch of the ophthalmic division of the 

 trigeminal nerve, but they reach the semilunar (Gasserian) 

 ganglion from the sympathetic plexus, which surrounds the 

 internal carotid artery (p. 186). The lacrimal secretion is 

 therefore diminished in paralysis of the ophthalmic nerve and 

 in lesions which involve the cervical sympathetic trunk in any 

 part of its course. 



It should be remembered that the gland does not begin to 

 secrete until the second or third month, and that its secretion 



