246 NORMAL HISTOLOGY. 



lines at varying distances from the poles ; and the 

 farther from one pole one end of the fibre is, the 

 nearer to the other will its other end lie. In the 

 young human lens, the lines from which the fibres 

 start may be seen on the anterior and posterior sur- 

 faces, under certain circumstances, in the form of a 

 three-rayed star ; in the adult, the rays usually part 

 at the end, giving rise to secondary rays. 



THE EYELIDS. 



These are formed in general by a plate of connec- 

 tive tissue, which toward the free border is very 

 dense and firm, and called the tarsal cartilage, or 

 tarsus ; they are covered on the outside by skin, on 

 the inside by the conjunctival mucous membrane ; 

 between the tarsus and the skin lie the bun- 

 dles of the musculus orbicularis. The tarsus, 

 which is, in no sense, cartilage, is a plate 

 of very dense and firm fibrillar connective tissue, 

 containing ordinary flattened connective-tissue cells, 

 and is closely connected within with the palpebral 

 conjunctiva. Imbedded within the tarsus lie the 

 Meibomian glands, thirty to forty in number in each 

 lid. They consist of numerous vesicular alveoli, 

 lined with short cylindrical cells, arranged along and 

 opening into long excretory ducts, which are lined 

 with laminated epithelium, and open on the inner 

 border of the edge of the lids. They are some, 

 what modified sebaceous glands, but, unlike most 



