THE EYE. 391 



[M. Langenbeck, some years ago described, in the free 

 portion of the zonula Zinnii, what he believes to be a muscnlar 

 ring, and terms the musculus compressor lentis s. accommoda- 

 torius ('Klinisch. Beitrage zur Ophthalmol./ 1849, p. 66), of 

 which I have been unable to perceive any indication. He has 

 probably confounded the zonular fibres with such a structure.] 



B. ACCESSORY ORGANS. 



§ 230. 



The eye-lids are supported by the so-termed tarsal cartilages 

 {tarsi) , thin, semilunar, flexible, but tolerably elastic plates, 

 attached internally and externally by the fibrous, tarsal liga- 

 ments, — and belonging, as far as their structure is concerned, 

 to the solid, fascicular, connective tissue, though occasionally 

 containing a certain number of minute cartilage cells. These 

 plates, 0*3 — 0-4"' thick, the fibres in which chiefly run parallel 

 with the borders, are covered externally by the orbicularis 

 palpebrarum and the integuments, and internally by the con- 

 junctiva. The skin is here very thin (i — I"'), with scanty, 

 subcutaneous connective tissue containing no fat, a delicate 

 cuticle, 0-055 — 0-058"' thick, and short papilla (of 0*60 — 

 0066 /// ); but it is furnished throughout with minute sudori- 

 parous glands (of -L — T V") and almost invariably, with numerous 

 minute hairs (frequently, with contiguous sebaceous glands, 

 but whether always so provided I do not know) . At the edges 

 of the palpebrce these hairs are more considerably developed 

 and constitute the eye-lashes, which are also furnished with 

 sebaceous follicles. Agreeing in all respects, in structure and 

 secretion, with the sebaceous glands, the Meibomian glands, 

 nevertheless, differ somewhat in form. They are imbedded in 

 the tarsal cartilages, to the number of from twenty to forty, in 

 the form of elongated, white, delicate, parallel, racemose fol- 

 licles, disposed in such a direction that the long axes of the 

 glands, cut those of the tarsal cartilages at a right angle. 

 Each of these glands, which are visible at once upon inverting 

 the eye-lid, and do not occupy the entire width of the tarsi, 

 consists of a straight excretory duct, 004 — , 05 /// wide, which 



