Alt — Glandular Structures Appertaining to the Human Eye. 197 



widens out more gradually. Where it makes the sudden 

 bend to form the horizontal part, it usually has a diverticle 

 (Fig. 56), which bulges out from its temporal side into the 

 tissue of the eyelid. This diverticle is formed just at the 

 end of the vertical part, and runs in a horizontal direction and 

 is sometimes comparatively large. Quite frequently there is 

 another diverticle in the horizontal part just at its beginning 

 which runs in a more vertical direction. 



The horizontal part of the upper canaliculus is about 7 

 mm. long and that of the lower canaliculus is a little longer. 

 As stated above, the course of this portion of the canaliculi 

 is not in reality horizontal, as the two gradually bend toward 

 each other. Moreover this part of the canaliculi does not run 

 in a straight line, so to speak, but is quite wavy, sometimes 

 even tortuous (Fig. 57). 



Just before reaching the temporal wall of the lacrymal sac 

 the two canaliculi may, and as a rule do, join together and 

 form one larger collective tube (Fig. 58). The length of this 

 tube varies materially in different individuals, and it may be 

 so short that it can hardly be recognized as a separate part. 

 In other cases the two canaliculi reach and enter the lacrymal 

 sac separately and ununited. 



From their beginning at the lacrymal puncta to their en- 

 trance into the lacrymal sac the canaliculi are formed by 

 a membrana propria, the connective tissue of which is largely 

 intermingled with elastic elements. This membrana propria 

 is lined with lamellated polygonal pavement epithelium 

 (Fig. 59) which often forms a dozen or even more layers, 

 seldom fewer than ten. 



By means of these canaliculi, as stated, the tear-fluid is 

 drained from the conjunctival sac into the larger receptacle, 

 the lacrymal sac, and again from this into the nose by means 

 of the nasal lacrymal duct. 



The lacrymal sac (Fig. 60), lies in the fossa lacrymalis 

 formed by the lacrymal bone and the frontal process of the 

 supram axillary bone, and between the branches of the internal 

 palpebral ligament. It forms a comparatively narrow, almost 

 slit-like, cavity, which has a great man} r diverticles and folds. 

 Its epithelium consists of a basal layer of more cuboid cells 



