44 Practicum VII. The Eyelids. 



8. Sensitiveness of the Conjunctiva. During life the conjunctiva is exquisitely 

 sensitive to irritation by small particles like dust or cinders, though more tolerant of the 

 contact of a larger surface like the finger-tip. Most operations on the eye are now ren- 

 dered painless, so far as concerns the conjunctiva, by the application of a few drops of a 

 solution of cocaine. 



a When a cinder or other irritating particle lodges upon the eye, 

 rubbing should be avoided. Hold the upper lid down with the finger- 

 tips applied at its edge. If after a few minutes the irritation does not 

 cease, hold the lids far apart and dash water upon the eye. If this fails 

 to wash the particle remove it as follows : Provide a rounded point like 

 that of a lead pencil that has been used a little. Before a mirror draw the 

 lower lid down ; if no foreign body is visible grasp the edge of the upper 

 lid firmly and turn it up, if necessary over a toothpick or pencil. When 

 the particle is seen, touch it lightly with the rounded point above men- 

 tioned and it will usually adhere to it. Of course the operation is more 

 easily performed by another person standing behind the seated patient, 

 and cocaine may be used if the conjunctiva is already inflamed or the 

 patient is very apprehensive ; but if cocaine were accessible a physician 

 could probably be consulted. It is worth bearing in mind that if the 

 irritating particle has been in the eye for some hours the inflammation 

 may persist even after its removal, so that the light should be excluded 

 by a bandage. 



b. For the inflammation above mentioned, or for dryness or redness 

 of the conjunctiva, a simple and harmless remedy is a solution of boracic 

 acid in water, five grains to the half-ounce (table-spoonful); when dis- 

 solved a few drops may be introduced either with a dropper or with the 

 tip of the finger applied at the mesal canthus, and repeated as frequently 

 as desired. 



9. The Plica. Transect the other lid at about its middle. When 

 the two lids are separated as far as possible there will be seen at one 

 canthus a semilunar fold, the PLICA (third eyelid or nictitating mem- 

 brane). This has already been seen in Pract. VI, and is outlined in 

 PI. XVI. 



a. The plica is at the mesal (nasal or "inner") canthus ; hence the 

 mesal and lateral aspects of the sheep's eye may be determined from it. 



b. The plica extends to about the middle of the "lower" lid, but 

 not so far along the "upper ;" hence from it may be also determined the 

 ventral and dorsal aspects of the eye. 



c. If, while a cat is sleeping, the lower lid be gently drawn down, 

 the plica may be seen partly covering the eye before it is withdrawn. 



d. The human plica (semilunaris] is an insignificant fold, an exam- 

 ple of vestigial organs. 



10. The Lachrymal Gland. On the dorso-lateral aspect of the eye 

 i. e , diagonally across from the plica, ectad of the conjunctiva, perhaps 

 covered in part by the cut margin of the skin of the upper lid, look for a 

 pale, lobulated mass much like the parotid gland (Pract. VI, 3, PI. XV). 

 Some or even all of it may have been cut away. This is the LACHRYMAL 

 GLAND ; its secretion, the tears, a thin, slightly saline liquid, is poured 

 upon the surface of the eye through ducts that open at or near the line 

 of reflection of the conjunctiva upon the ball. 



11. The Lachrymal Canals. Transect the skin about i cm. from 

 the mesal canthus. Examine the loose tissue just entad of the skin for a 

 pair of holes about 3 mm. apart. Pass the probe into either and it will 

 emerge at the margin of the lid about 3 mm. from the canthus. Repeat 



