Tlll-I KYl'IHALL AM) ITS Sfl{l)C.\])l\GS 1021 



with the eyes looking straight forwards, the lower mai-inn of the upjx-r lid is nearly 

 opposite to the top of the cornea, or, more strictly, to a line midway liet \\ecn the 

 top of the cornea and the up|K>r border of the pupil, while the lower fid corresponds 

 with the lower conical margin. When the eyes are directed stronglv upwards, the 

 upper lid is relatively on ;i slightly higher level, as it is simultaneously raised, but 

 the lower lid now leaves a strip of sclerotic exposed below the cornea. On looking 

 downwards the upper lid covers the upper part of the cornea as low down as the 

 level of the top of the pupil, while the lower lid is about midway between the pupil 

 and the lower corneal border. 



If we draw the eyelids forcibly apart, we expose the whole cornea, and a zone 

 of sclerotic about eight and a half millimetres in breadth above and below, and ten 

 millimetres in breadth to the outer and inner sides altogether about one-third of 

 the globe; all the eyeball thus exposed is covered by the ocular conjunctiva. Over 

 the sclerotic the conjunctiva is freely movable, and through it we see superficial 

 blood-vessels that can be made to slip from side to side along with it (conjunctival 

 vessels). Occasionally other deeper vessels may also be seen which do not move 

 with the conjunctiva, but are attached to the sclerotic (anterior ciliary arteries and 

 veins). Near the corneal border the conjunctiva ceases to be freely movable, and 

 it is closely adherent to the whole anterior surface of the cornea, giving the latter 

 its characteristic bright, reflecting appearance; no blood-vessels are visible through 

 it here in health. (When the lids are shut, the space enclosed between their pos- 



Fio. 723. VIEW OF EYEBALL, ETC., OBTAINED ON DRAWING THE LIDS FORCIBLY APART. 



(After Merkel, slightly modified.) 



SEMILUNAR FOLD 

 UPPER LACHRYMAL PUNCTUM 

 CARUNCLE 

 LOWER LACHRYMAL PUNCTUM 



OPENINGS OF TARSAL QUNOS -JS^^' "^^^ INFERIOR CONJUNCTIVA!. FORN.K 



terior surfaces and the front of the eyeball is thus everywhere covered by conjunc- 

 tiva, and is known as the conjunctival sac.) 



Not unfrequently the tendinous insertions of some or all of the recti muscles 

 into the sclerotic may be seen through the conjunctiva, each insertion appearing as 

 a series of whitish parallel lines running towards, but terminating about seven 

 millimetres from, the corresponding corneal border. The cornea appears as a 

 transparent dome, having a curvature greater than that of the sclerotic; the junc- 

 tion of the two unequally curved surfaces is marked by a shallow depression run- 

 ning around the cornea, known as the scleral sulcus. In outline the cornea is 

 nearly circular, but its horizontal diameter is slightly greater than its vertical. 

 Between it and the iris a space exists, whose depth we can estimate roughly by looking 

 at the eye from one side; this space, or anterior chamber, is occupied by a clear 

 fluid, the aqueous humour. Almost the whole anterior surface of the iris is visible, 

 its extreme periphery only being concealed by sclerotic. In colour the iris varies 

 greatly in different individuals. Near its centre (really a little up and in) a round 

 hole exists in the iris, the black pupil, whose size varies considerably in different 

 eyes, and in the same eye according to temporary conditions, such as exposure to 

 light, etc. 



In examining the surface-markings of the living iris, one of dark colour is to be preferred. 

 Focal illumination will be found useful, for which purpose a second convex lens will be required. 



On the surface of the iris we see a number of ridges running more or less radially; 

 adjoining ones occasionally unite and interlace to some extent, so as to leave large 



