APPENDAGES OF THE EYE 



681 



double layer. As the duct approaches the conjunctiva! surface the 

 number of cell layers increases until their lining epitheliumfinally 

 comes to resemble 

 the stratified epi- 

 thelium of the con- 

 junctiva with which 

 it is continuous. 



Minute collec- 

 tions of diffuse 

 lymphoid tissue 

 and even small 

 lymph nodules are 

 occasionally found 

 just beneath the 

 epithelium of t h e 

 conjunctiva in the 

 neighborhood of the 

 lacrimal glands of 

 the f ornix ; occa- 

 sionally the lym- 

 phoid tissue is 

 quite abundant. 



In animals pos- 

 sessing a membrana 

 nictitans ('third 

 lid') a small, mu- 

 cus-secreting gland 

 occurs at the inner 

 angle of the orbit; 

 this is known as the 

 gland of Harder. 

 It is well developed 

 also in some mam- 

 mals, e.g., rabbit, 

 but in man and 

 other primates it is 

 usually absent, though in an extremely vestigial condition it may occa- 

 sionally be found within the basal portion of the plica semilunaris. 



FIG. 570. PORTIONS OF Two ADJACENT LOBULES OF THE 

 LACRIMAL GLAND OF THE RABBIT, SHOWING Two STAGES 

 IN SECRETORY ACTIVITY OF THE TUBULES. Magnifica- 

 tion X 100. 

 In the upper lobule the cells are filled with minute, in 



the lower lobule with large, secretion spherules. 



43 



