368 SENSITIVE SYSTEM. 



fibrous substance is the expanded tendon of the levator palpebrcz 

 superioris. It may be traced completely over the tarsal carti- 

 lages : indeed, we only lose sight of it when we come to the bor- 

 der of the lid. 



Tarsal Cartilages. 

 The tarsi or tarsal cartilages are the substances imparting 

 that firmness and elasticity to the borders of the lids which we 

 have already had occasion to notice. There are two of them, a 

 superior and an inferior: the superior tarsus is the broader and 

 more convex cartilage ; for, in fact, they correspond nearly in 

 shape and size to their respective lids. They are convex out- 

 wardly ; concave, in order to embrace the ball, inwardly. They 

 possess thick and firm ciliary margins ; but grow thin as they 

 recede from the borders of the lids, and end in fibrous expansions, 

 which, from connecting them to the rim of the orbit, have got 

 the name of the tarsal ligaments. The tarsus is fibro-cartila- 

 ginous in texture ; but it is so intimately united with the tendon 

 of the levator and beset with the ducts of the ciliary glands, that 

 it can scarcely be said to be demonstrable in a separate and per- 

 fect state : in short, the tarsi are the flexible shapes upon which 

 the other soft parts are stretched and moulded^ preserving by 

 their elasticity the form of the lids, keeping them in constant 

 apposition with the eyeball, and serving to approximate them 

 when not counteracted by muscular force. The stifl^ening thus 

 imparted to the lid also proves the means of preserving the ar- 

 rangement of the eyelash ; for, without it, the hairs would be 

 apt to run across one another. At this stage of the dissection 

 we gain a view of 



The Ciliary or Meibomian Glands. 



These are so many little white follicular bodies, whose canals 

 are large enough to admit a pin, vertically ranged in parallel 

 lines like the pipes of an organ along the borders of the lids, 

 within grooves made for their reception in the concave part of 

 the tarsal cartilages. They are distinctly visible, when the lids 

 are everted, through the thin lining membrane. They vary 

 somewhat in caliber, but more in length ; being longer in the 

 upper than in the lower lid. Viewed through a microscope, 

 each row (upper and under) is found to consist of a congeries of 

 very small spheroid bodies, every one of which is considered to 

 be a distinct gland, and to possess an excretory duct. They 

 secrete an unctuous matter — a suety sort of oil, which may be 

 squeezed out from the mouths of their ducts, the ciliary orijices, 

 in taper portions resembhng small white worms. This secretion 



