66 THE EMBRYOLOGY OF THE EYE. 



While the Meibomian glands are develop- 

 ing, the mesoblastic tissue forms a dense sheath 

 of spindle-cells about them. This sheath be- 

 comes denser and forms a very tough fibrous 

 layer in which the glands lie imbedded — the 

 tarsus. Between the tarsus and the posterior 

 epithelium there is only a trace of loose con- 

 nective tissue, but beneath the external epithe- 

 lium there is a thin layer of loosely meshed 

 tissue without fat cells. The epithelium join- 

 ing the lid margins degenerates, and the cilia 

 pushing through break it up and the lids 

 separate. 



Lachrymal apparatus. In the young foetus 

 there is a groove between the lateral nasal 

 process and the superior maxillary process, 

 extending from the eye to the nostril, and 

 called the lachrymal furrow (Fig. 19, A and B). 

 This furrow soon disappears, and we see only 

 a trace of its former existence near the eye 

 (Fig. 19, C). In frontal sections at the stage 

 shown in Fig. 19, A, B, we find a short dis- 

 tance from the nostril a thickening of the epi- 



