BLOOD-VESSELS OF THE EYELIDS. 5 



Meibomian glands (fig. 2, &). Their minute ducts open near the line of reflection 

 of the conjunctiva upon the globe of the eye. 



Harderian g-land. All animals which possess a well-developed membrana nictitans have 

 also, situated at the mesial angle of the eye, a special gland, the duct of which opens beneath 

 the third eyelid. The gland has a racemose structure, and secretes a mucus-like fluid, thus 

 differing from the serous-secreting lachrymal. It is not found in primates, unless in an 

 extremely vestigial form. 



The ocular portion. The conjunctiva changes its character at the line of reflec- 

 tion from the eyelids, becoming thinner and being loosely connected to the sclerotic 

 coat of the eyeball by submucous tissue. But over the cornea it consists only of a 

 prolongation of the epithelium, which is closely adherent to the anterior layers of the 

 cornea, in connection with which it will be described. 



Blood-vessels. The blood is supplied to the eyelids mainly by the internal and 

 external palpebral arteries ; the former being derived from the ophthalmic artery 



Pronto-nasal 

 -Superior paljgebral 



Transverse, 

 faciai" 



Infra-orbital 



ligament 

 Fig. 4. DISSECTION SHOWING THE ARTERIES AND VEINS OF THE EYELIDS. (After Testut. ) 



and the latter from its branch, the lachrymal. The internal palpebral are usually the 

 larger, and consist of two vessels, a superior and an inferior, one for each lid, which 

 they reach by piercing the palpebral fascia, one a little above and the other just 

 below the mesial palpebral ligament (fig. 4). In the eyelid each vessel runs with a 

 tortuous course near the free border between the tarsus and the bundles of the 

 orbicularis, forming the so-called tarsal arches. At the outer side they anastomose 

 with the external palpebrals, which are derived from the lachrymal. The superficial 

 temporal and transverse facial also send branches to join this anastomotic chain at 

 the outer part of the orbit. 



In the upper eyelid there is a secondary arterial arch formed by a branch of the 

 superior palpebral, and running just in front of the upper or attached end of the 

 tarsus, between the tendon of the levator palpebrae and the plain muscular sheet 

 which passes from it to join the tarsus. Sometimes there is a similar secondary arch 



