116 
ON THE STRUCTURE OF THE EYE 
gular form of the osseous plate of the sclerotic coat. The 
sphericity of the retina within is not interrupted by this ir- 
regular form of the external coat, as there are several soft 
parts interposed between them. The conjunctiva is black, 
like the skin of the animal, to the margin of the transparent 
cornea. The pupil is irregularly circular, as in many other 
fishes. The iris has a greenish-white colour, and a beauti- 
ful metallic lustre. The cornea is flat, and about If inch 
in diameter. The anterior edge of the osseous plate pro- 
jects beyond the margin of the cornea, so as to make the 
anterior part of the eye a little concave externally. There 
is no eyelid, but a looseness of the conjunctiva round the 
edge of the orbit, to admit of the motions of the eye. The 
conjunctiva does not pass loosely over the cornea, as in the 
haddock and many other fishes, but adheres so strongly as 
only to be separated from it with difficulty, after long ma- 
ceration. The muscles of the eyeball are very strong and 
red coloured, like those of a quadruped, and correspond 
with the extensive distribution of the red globules of the 
bbod through the other parts * of this animal. The adipose 
substance, in which the eye is imbedded, is very different 
from the soft white watery substance we usually find in this 
situation in smaller fishes. It is firm, of a yellowish-white 
colour, and filled with an oily matter, which agrees much 
in its smell, colour, and other properties, with the oil pra- 
cured from the whale. 
The tunica conjunctiva can be separated with ease from 
the surface of the sclerotic as far as the margin of the cor- 
nea, where it is firmly connected with the projecting edge 
of the osseous plate. After long maceration, it can be torn 
* See my account of the anatomy of the thoracic and abdominal vis- 
cera of the Swordfish, in the Transactions of the Medico-Chirurgical 
Society of Edinburgh, vol. iii. 
