AND PHYSIOLOGY. 



375 



hardened and partially divided into segments by an immersion 

 in alcohol. 



687. V i t r eons,— The Vitreous Humor (from its resem- 

 blance to glass) is of the form of a sphere, with the anterior 

 portion removed, and constitutes seven eighths of the globe of 

 the eye. It is a transparent fluid enclosed in a transparent 

 membrane, and through its central portion from the entrance 

 of the optic nerve, there passes a small artery to the lens, 

 which supplies it with blood. 



688. Lachrymal Gland.— Nasal Duel. — At the outer angle 

 of each eye is found a gland called the Lachrymal gland, nearly 

 three fourths of an inch in length, and of a flattened oval 



Fig. 348. 



Posterior View of the Eyelids and Lachrymal G-land. 1, 1, Orbicularis Palbebrarum 

 Muscle. 2, Borders of the Lids. 3, Lachrymal Gland. 4, Its Ducts opening in the Up- 

 per Lid. 5, Conjunctiva covering the Lids. 6, Puncta Lachrymalia. 7, Lachrymal Ca- 

 runcle as seen from behind. 



shape. (Fig. 348.) Passing from this gland to the eye, are from 

 eight to twelve small ducts, which open upon the under side 

 of the lid near its edge, about one twentieth of an inch apart, 

 w r hich carry the tears to the eye. By continual winking this 



687. From what does the vitreous humor get its name? Describe it. CSS. Where are 

 the lachrymal glands situated? What is their size ? How many ducts have they ? What 

 do they secrete ? Of what use is winking? 



