1446 HUMAN ANATOMY. 



former receives lymph from the skin and muscles, the latter from the Meibomian 

 glands and the conjunctiva. The larger vessels on the outer side pass to the pre- 

 auricular and parotid lymph-nodes, and those on the inner or mesial side follow the 

 tributaries of the facial vein and enter the submaxillary lymph-nodes. 



Nerves of the Eyelids. — The sensory nerves are branches of the ophthalmic 

 and superior maxillary divisions of the trigeminal. The upper lid is supplied mainly by 

 the frontal and supraorbital nerves, the lower lid by the infraorbital nerve. On the 

 nasal side these nerves are supplemented by twigs from the supra- and infratrochlear 

 branches of the ophthalmic, and on the outer side by terminal filaments from the 

 lachrymal nerve. The main branches lie between the tarsi and the orbicularis 

 muscle, sending branches forward to the skin and backward through the tarsi to the 

 conjunctiva and Meibomian glands. In addition a marginal plexus is formed near 

 the edge of each lid, which supplies the adjacent parts and the follicles of the cilia. 



The motor nerve to the levator palpebrae is a branch of the superior division of 

 the oculomotor nerve ; the orbicularis palpebrarum is supplied by the facial, and the 

 involuntary muscle of the lids by fibres from the sympathetic. 



Practical Considerations. — The Eyebrows. — The hair of the eyebrows may 

 be absent, dark brows may show white patches (piebald eyes), or they may be 

 entirely white, as in albinos. Incisions in this area, as for neurectomy in supra- 

 orbital neuralgia, should be made in the line of the brow and within the limits of the 

 hair, so that the scar which results may be hidden. 



Dermoid cysts occur in the line of the orbito-nasal fissure of the foetus, and are 

 most frequent near the outer end of the brow, under the orbicularis palpebrarum, 

 next to the periosteum. Usually they are no larger than a cherry, and in some 

 instances lie deep in the orbit, when they would be difificult of diagnosis. More 

 rarely they occur at the inner angle of the orbit, when they may be connected with 

 the dura. In such cases they would be difficult of removal and might be confused 

 with meningoceles. 



Epicantlms is a crescentic fold of skin lying over the inner canthus and the 

 inner end of the palpebral fissure. It may be associated with a congenital defect in 

 the bridge of the nose. In many children a slight tendency to it is seen before the 

 bridge of the nose has reached its full development, while in those races which have 

 little or no bridges to their noses, a slight epicanthus is normal. Until this condition 

 is suspected, these children are often thought to have convergent squint, because 

 the cornea is nearer to the skin than in a normal eye. 



Very rarely the lids may fail to develop (ablepharia) ; less rarely a cleft in the 

 margin of the lid is seen, usually to the median side of the centre of the lid (colo  

 boma), and most frequently in the upper lid. Sometimes the eye has a uniform 

 covering of skin which replaces the lids, no palpebral fissure being present. This 

 is probably due to a persistence of the early foetal condition, in which the two lids 

 are adherent. It is called ankylo-blepharon. 



Lagophtliahmis is an incomplete closure of the lids, and is sometimes congenital, 

 sometimes the result of paralysis of the facial nerve which supplies the orbicularis 

 muscle. Voluntary contraction of this muscle will usually close the lids in the les^r 

 degrees of the congenital variety, but in sleep they are not closed. Since the eye 

 turns up as the lids are brought together, the cornea is in large part concealed. 



Ptosis is a drooping of the upper lid, and when congenital is usually associated 

 with epicanthus, and is bilateral. The forehead is often wrinkled from the eftort of 

 the occipito-frontalis muscle to aid the orbicularis in lifting the lid. The head is 

 usually thrown back and the eyes depressed to bring the sensitive part of the retina 

 and pupil in line with the object to be seen. 



Blepharospasm is an irritable spasm of the orbicularis closing the lids, and is 

 usually due to disease of other parts of the eye. 



The skin of the lids is the thinnest in the body and is very loosely applied, 

 through the loose areolar subcutaneous tissue. It therefore wrinkles easily, is readily 

 deformed by scars, and is a favorable field for plastic operations. If cicatricial con- 

 traction everts the lower lid, as it often does, the condition is known as ectropion. 

 More rarely contraction of the conjunctiva after ulceration or injury inverts a lid, 



