CHAPTER XLII. 

 THE ORBIT. 



ANATOMY. EFFECTS OF INJURY TO 



ORBITAL NERVES. 



The Eyelid. The structures composing the eyelid, 

 from without inwards, are : Integument, superficial fascia, 

 orbicularis palpebrarum muscle, connective tissue, tarsal 

 cartilage, subconjunctival tissue, and conjunctiva. In the 

 margin of the lid are the eyelashes and the sebaceous 

 glands connected with them, modified sweat glands and 

 the ducts of the Meibomian glands. 



Lachrymal apparatus. Situated at the upper and 

 outer part of the orbit and supported there by a division 

 of the orbital fascia is the lachrymal gland with its ex- 

 cretory ducts, while, near the inner canthus are the puncta 

 lachrymalia, each opening upon the summit of a papilla. 

 These puncta open into the upper and lower canal iculi, 

 which, passing more or less horizontally, convey the tears, 

 jsecreted by the lachrymal gland, to the lachrymal sac. 

 This sac is situated in a depression in the lachrymal bone 

 at the inner angle of the orbit and is nearly half an inch in 

 length. It is continuous with the nasal duct, and this 

 duct is about half an inch in length and opens into the up- 

 per end of the inferior meatus of the nose, just beneath 

 the upper border of the inferior turbinated bone. The 

 mucous membrane of the lachrymal canal is continuous 

 with the conjunctiva above and with the nasal mucous 

 membrane below, and the direction taken by a probe in 

 following the canal is downwards and slightly backwards 

 and outwards. The orbit is about one and three-quarter 

 inches in length, and' contains the eyeball embedded in the 

 orbital fat. Its base measures about one and a quarter 



