VISUAL ORGAN. 361 



(6) Protecting Organs of the Eye. 

 (1) The Eyelids and the Conjunctiva. 



The skin which covers the outer surface of the eyelids 

 passes over into the conjunctiva palpebralis, which lines the 

 inner surface. Between these two layers we find the main por- 

 tion of the eyelid, which contains the m. orbicularis palpe- 

 brarum and the tarsus. The relation of these constituents is 

 shown best in a sagittal section of the lid, as represented in 

 Fig. 268. 



On the outer surface the skin is thin and contains numerous 

 fine hairs, small sebaceous glands, and sweat glands. The 

 papillae of the corium are small and weakly developed, with the 

 exception of those at the edge of the lid. The subcutaneous 

 tissue is very loose and poor in fat cells. Along the anterior 

 border of the lid there are thick hairs, the eyelashes, arranged 

 in two or three rows and deeply sunk in the corium. 



In connection with the eyelashes at the border of the lid we 

 find two kinds of glands : the ordinary small sebaceous glands, 

 and Moll's glands (glandule ciliares). The latter resemble the 

 coil glands in form. Their ducts open often into the follicles 

 of the eyelashes. 



Behind the subcutaneous tissue there lies a layer of cross- 

 striated muscle, the m. orbicularis palpebrarum, whose bundles 

 run from one angle of the lid to the other. In a sagittal section 

 the bundles are cut transversely. Near the border of the lid, 

 behind the eyelashes, lies the musculus tarsatis (Riolani). 



Farther in, there is a layer of connective tissue (fascia palpe- 

 bralis), with which the tendon of the muse, levator palpebrce in 

 the upper lid is fused. A part of this muscle, which also con- 

 tains smooth muscle cells (m. palpebralis superior), is attached 

 to the tarsus. In the lower lid we find in this region the ten- 

 don of the m. rectus inferior, of which the m. palpebralis in- 

 ferior is a process. The latter contains smooth muscle cells. 



Farther back, there occurs a firm plate of fibrous connective 

 tissue, the so-called tarsus, which occupies about two-thirds of 

 the height of the whole eyelid. It contains about thirty tarsal 



