STRUCTURE OF THE EYELIDS. 447 



(when fresh) cellular bodies of columnar or cubical form, which 

 become deeply stained with carmine and chloride of gold, and 

 which are in immediate contact with the membrana propria. 



The lowermost tier of cells, composed of cubic or columnar 

 cells, and the uppermost tier, composed of flattened cells, are 

 prolonged into the secondary excretory ducts of the several 

 acini. In each acinus the presence of a membrana propria 

 may be distinguished, which sometimes appears to be struc- 

 tureless, and sometimes (in specimens prepared with chloride 

 of gold) to be provided with a network of flat branched struc- 

 tures. The membrana propria is lined by a layer of granu- 

 lated cubical or short columnar cells, which stain easily and 

 deeply, and contain spheroidal nuclei in their interior. This 

 layer of cells is a direct continuation of the deepest cell layer 

 of the excretory duct. The interior of the acinus is filled with 

 sharply defined bodies flattened by mutual pressure, which in- 

 crease in size towards the interior of the acinus, and when 

 fresh appear to be uniformly filled with a highly refractile 

 substance (fat). If these bodies are examined in specimens 

 which have previously been immersed in alcohol and oil of 

 cloves, and then mounted in dammar resin, each of them 

 presents a sharply defined nucleus, and in some cases also an 

 extremely fine network in their interior. 



Near the fornix conjunctive, and in the portion of the sub- 

 mucous tissue termed the tarsus, lie certain gland tubes which 

 probably secrete mucus, and are extraordinarily convoluted. 



The gland tube is bounded by a membrana propria, on 

 which in general there is only a single layer of columnar 

 granular cells, though occasionally there appear to be two rows 

 of tesselated cells. The short excretory duct of the gland, 

 which exhibits the same structure, perforates the mucous 

 membrane of the conjunctiva obliquely, in order to open into 

 the sac of the conjunctiva. 



These glands probably correspond to the acinous mucous 

 glands described by Krause and Sappey as situated at the line 

 of transition of the conjunctiva palpebrarum into the fornix. 



The posterior layer of the lid, the conjunctiva, when fresh, 

 is of a delicate pink colour, and presents a velvety surface. It 

 is not everywhere of equal thickness, but increases in this 



