OF THE SPERM WHALE. 
121 
tinct from the conjunctiva, since around the extent it 
occupies it terminates by an irregular margin, and is 
capable of being detached from the conjunctiva, when it 
presents the form of a delicate layer of cuticle, with a 
black pigment deposited beneath its surface.* 
“ The cornea of the cachalot is dense, and composed of 
many layers ; when divided, a small quantity of limpid 
aqueous humour flows forth : the anterior chamber of the 
eye is very limited, and the crystalline lens projects into 
it through the pupillary aperture. The iris is a coarse 
membrane of a dull-brown colour, with a narrow zone of 
lighter hue surrounding its outer margin. Its inner and 
free margin is very thin, and embraces the protruding 
convexity of the lens. 
* 
“ The lens is small, certainly not exceeding in size 
that of the human eye: it forms nearly a perfect sphere: 
the vitreous humour tolerably abundant. The retina 
was spread with beautifully delicate arborescent vesselsj 
and afforded a small bright spot at the insertion of the 
optic nerve. Beneath the retina was spread a tapetum 
of dense membranous texture and yellow-green or erugo- 
green colour. The sclerotic at its posterior third is thick, 
fibrous, and resisting, whilst its anterior third is thin and 
flexible; no lachrymal apparatus exists.” 
* A slight dark tint around the cornea is not uncommon amongst 
the dark-skinned natives of warm countries. 
* 
G 
