204 HOUSE, GARDEN, AND FIELD 



On the edge of the lower eyelid, not far from the inner 

 angle of the eye, there can be seen a small but distinct 

 prominence. Just above it, on the corresponding part of 

 the upper eyelid, is another prominence of the same size. 

 Your concave mirror will show you that each prominence 

 is perforated by a small hole. The holes are the openings 

 of canals, which soon unite, and open into a larger duct, 

 this passes straight downwards, and discharges into the 

 lower part of the nose. A watery secretion, discharged 

 from the tear-gland, is employed to moisten the eyeball 

 and eyelids, and wash away dust. The secretion, after 

 bathing the parts, escapes through the ducts just de- 

 scribed, leaving behind the dust, which accumulates in 

 the neighbourhood of the eye- wart. The insensible flow 

 of water escapes into the nose, but when irritation of the 

 eye or strong emotion causes profuse secretion, the eye 

 overflows, and we shed tears. 



Sit so as to face a strong light, turn either the upper 

 or lower eyelid outwards, and examine its inner surface ; 

 you will be able to see through a thin, transparent 

 membrane the Meibomian glands. It is rather easier to 

 see them in the eye of a second person. The glands look 

 like white, beaded strings, and run at right angles to the 

 edges of the eyelid ; there are about thirty on the upper 

 eyelid, and rather fewer on the lower one. Each gland 

 opens separately on the free edge of the eyelid, and the 

 openings may be made out with the help of the concave 

 mirror. The glands are filled with an oily secretion, and 

 it is supposed that they hinder adhesion of the lids, such 

 as might be caused by hardened mucus. Is it possible 

 that the oily secretion checks the overflow of the watery 

 fluid which bathes the eyeball ? 



The face is a chief organ of expression, and we glance 

 first at the face of a companion when we want to know 

 the state of his mind. Even a dog will look into his 

 master's face as if to read there the indications of satis- 

 faction or displeasure, though our voice and gestures tell 



