WILSON — ON THE EYE OF THE SEAL. 219 



ternal surface. The inner surface of the anterior portion has connected 

 and intimately attached to it the ciliary muscle, which is also of rather 

 a wedge shape, T x w wide ; it appears composed of simple fibres and 

 connective tissue, the fibres taking a direction from without backwards 

 and inwards towards the choroid. More accurately described, this 

 muscle appears to consist of two separate and distinct bundles of fibres 

 — one proceeding fx*om the cornea, the other from the iris, and joining 

 posteriorly, and leaving between them anteriorly the space known as 

 the canal of Fontana, which space is, I believe, larger in the Seal than 

 in any other animal. The external part of this muscle is that by means 

 of which the curvature of the cornea was said by Sir Philip Crampton 

 (its discoverer) to be altered. These parts are well seen in the section 

 on the table, which has been prepared by steeping in chromic acid. In 

 the same specimen, too, the fibres running from the cornea to the scle- 

 rotic may be seen with the unassisted eye. This muscle has attached to 

 it, and assists in forming the suspensory ligament of the lens, and in 

 front the pillars of the iris. The choroid gradually gets thin from be- 

 hind forwards until it reaches the thin portion of the sclerotic, from 

 whence it continues inwards and forwards, and forms the ciliary pro- 

 cesses. The retina ceases at, or rather a little behind, the thinnest part 

 of the sclerotic, at the ora serrata. The lens is large, and almost globu- 

 lar; its posterior surface is, however, more convex than its anterior ; its 

 measurements are, as well as I can judge — antero-posterior diameter, 

 \ inch ; lateral diameter, T °g- inch. The cornea is somewhat flattened, 

 large, and larger from side to side than from above downwards. It is 

 overlapped externally by the sclerotic. The iris is of a rich, soft brown 

 colour ; the pupil wide, and rather circular, and placed somewhat at the 

 nasal side. The animal possesses a nictitating or third eyelid, which is 

 large and moveable ; it also has a small retractor or suspensory muscle — 

 a muscle well developed in the ruminants, and in some carnivora — 

 arising from the optic foramen, and inserted by four small muscles into 

 the sclerotic, f in front of optic nerve. There are two obliqui and four 

 recti muscles, which latter give me the idea of each dividing into two, 

 one of which is inserted into the anterior segment of the sclerotic, be- 

 hind the cornea ; the other appears to advance to the tegumentary ap- 

 paratus of the eye, into which it is inserted ; of this disposition of parts, 

 however, I cannot speak with confidence, as I have not had an oppor- 

 tunity of seeing the parts in situ. 



Various theories have been published to explain how distantial ad- 

 justment occurs. If our eyes are healthy and normal, we can see clearly 

 and well one and the same object at various distances; our eye adjusts 

 itself to near and distant objects generally without any appreciable effort 

 on our part. The rays of light from a given object must be refracted 

 through the transparent media of the eye, and must come to a focus in 

 the retina or nervous expansion. If from any cause this focus fall 

 either in front of or behind the retina, indistinct vision ensues (if the 

 focus fall in front of the retina, short sight ; if behind the retina, long 



