196 Trans. Acad. Sci. of St. Louis. 



against staining reagents and more especially they do not show 

 any staining affinity which would prove that they are of a 

 muciparous character. 



Their short excretory ducts are lined with cylindrical epi- 

 thelium, and their external orifice lies either on the surface 

 of the lacrymal caruncle or in the plica semilunaris. 



Aside from these glandular structures, usually some fat- 

 tissue is inclosed in the connective tissue which forms the 

 body of the caruncle. In one case, and in one only, I 

 found a small amount of hyaline cartilage tissue embedded in 

 the loose connective tissue near the lower margin of the 

 lacrymal caruncle and between it and the plica semilunaris 

 (Figs. 51, 52). 



THE LACRYMAL DRAINAGE APPARATUS. 



The tear fluid which has neither been evaporated nor used 

 up in moistening the surfaces of the eyeball and the eyelids, 

 is drained off into the nose at the nasal angle of the palpebral 

 fissure by means of a special system of draining tubes. 



This draining apparatus begins with the lacrymal puncta, 

 two small oval openings which are situated at the apex of the 

 lacrymal papillae. These papillae are little cone-shaped ele- 

 vations which lie in the lidmargins in line with, and to the 

 nasal side of, the orifices of the Meibomian glands in the 

 tarsal part of the eye-lids. The lower papilla lies, as a rule, 

 a little farther removed temporally from the inner canthus, 

 than the upper one. 



From the puncta the lacrymal canaliculi start by which the 

 tear-fluid is carried to the lacrymal sac. Each canaliculus 

 may be divided into two parts, namely, a more or less vertical 

 (Fig. 53) and a more or less horizontal one (Fig. 54). The 

 first part, which is by far the shorter, runs from the lacrymal 

 punctum upwards (in the lower eyelids downwards), and in- 

 wards, nearly at a right angle to the lidmargin. It is from 

 1.5 to 2 mm. long. The second, the so-called horizontal, 

 part, runs in the direction towards the nose until it reaches 

 the lacrymal sac. 



Just inwards from its orifice at the lacrymal punctum the 

 vertical part is generally very narrow (Fig. 55), and then 



