DISSECTING MANUAL. 



part (substantia corticalis), and a dense central part (nucleus 

 lentis). The centres of its surfaces are its anterior and pos- 

 terior poles; its circumference is known as its equator. The 

 aqueous humor is a watery fluid which fills the anterior and 

 posterior chambers. [735] 



Eyelids. These are two skin folds, separated by a fissure 

 (palpebral) which ends in inner and outer angles (canthi) ; in 

 the triangular space (lacus lacrimalis) between them inter- 

 nally is seen a pale red body (caruncula lacrimalis) ; a papilla 

 (lachrymal) lies on the margin of each lid at the outer limit of 

 the lacus lacrimalis. Mucous membrane (conjunctiva) lines 

 the lids, forms a vertical fold (plica semilunaris) between the 

 eyeball and caruncula, and also passes onto the eyeball. A 

 fibrous plate (tarsal plate) is found in each lid. The external 

 tarsal ligament is attached to the malar bone; and the internal 

 to the nasal process of the superior maxilla in front of the 

 lachrymal groove; their free ends divide and are attached to 

 the ends of the tarsal plates. Membranous expansions (su- 

 perior and inferior palpebral ligaments) run from each mar- 

 gin of the orbit to the corresponding tarsal plate; they fuse 

 externally with the external tarsal ligament, but pass internally 

 behind the internal tarsal ligament to the lachrymal bone be- 

 hind the lachrymal sac. Meibomian glands lie behind the tar- 

 sal plates and open on the margins of the lids, behind the 

 lashes. [738] 



Lachrymal Apparatus. The lachrymal gland is an oval body 

 lying in the upper and outer part of the orbital cavity; it con- 

 sists of two portions partly separated by an expansion of the 

 Levator palpebrae superioris tendon. The orbital portion is 

 the larger and lies in the fossa lacrimalis of the frontal; its 

 ducts receive those of the palpebral portion and empty on the 

 upper eyelid close to the line (fornix) of reflexion of the con- 

 junctiva. The palpebral portion lies below and in front, pro- 

 jecting into the upper eyelid. The lachrymal canals begin by 

 minute orifices (puncta lacrimalia) at the apices of the lach- 



[58] 



