DISSECTION OF THE. EVE; 87 
the eyelids to the eyeball is known as the forzzx con- 
junctive. The portion of the conjunctiva upon the 
eyeball can be followed forward easily as far as the 
cornea. Upon the cornea itself it is reduced to a 
simple layer of stratified epithelial cells firmly adherent 
to the proper substance of the cornea, and visible only 
in microscopic sections. 
4. The Membrana Nictitans. The third eyelid or 
nictitating membrane is very conspicuous in the dog. 
It is formed by a fold of the conjunctiva strengthened 
by a lamina of cartilage, and projects from the inner 
angle of the eye. In the dead animal it may extend 
over one third or one half of the exposed portion of 
the eyeball. In the human eye this membrane is re- 
duced to a comparatively inconspicuous fold, the A/zca 
semilunares. 
5. The Harderian Gland. ‘This gland lies on the 
inner face of the nictitating membrane. It is easily 
exposed by everting the membrane. It is not present 
in man. 
6. The Puncta Lacrymalia. On the free edge of 
eachmevelid, about 2 mm. or more from the inner 
canthus of the eye, are the mouths of two small ducts. 
Each begins as a small opening on the edge of the 
lid which leads into a short canal. The two canals 
end in an expanded portion known as the lachrymal 
sac, from which the zasa/ duct is continued downward 
to open into the lower portion of the nasal cavity. 
By means of this apparatus the tears which moisten 
the front of the eyeball are drained off into the nose, 
and thence into the pharynx. 
7. The Lachrymal Gland. To expose the tear-gland 
cut through the skin and conjunctiva outward from 
the outer canthus for a short distance, and then 
