anatomy and physiology 
its union with the cornea, where it is thin and soft. It 
is extremely firm in its texture where thick, and from a 
transverse section would seem to be composed of ten- 
dinous fibres, intermixed with something like cartilage ; 
in this section four passages for vessels remain open. 
This firmness of texture precludes all effect of the 
straight muscles on the globe of the eye by altering its 
shape and adapting its focus to different distances of 
objects, as has been supposed to be the case in the human 
eye. The cornea makes rather a longer ellipsis than the 
bail of the eye, the sides of which are not equally curved, 
the upper being most considerably so. It is a segment 
of a circle somewhat smaller than that of the eyeball— 
is soft and very flaccid. The tunica choroides resembles 
that of the quadruped, and its inner surface is of a silver 
hue, without any nigrum pigmentum. The nigrum pig- 
mentum only covers the ciliary processes, and lines the 
inside of the iris. The retina appears to be nearly 
similar to that of the quadruped. The arteries going to 
the coats of the eye form a plexus passing round the 
optic nerve, resembling in its appearance that of the 
spermatic artery in the bull and some other animals. 
The crystalline humour resembles that of the quadruped, 
but whether it is very convex or flattened I cannot 
determine, those I have examined having been kept too 
long to preserve their exact shape and size. The vitreous 
humour adhered to the retina at the entrance of the 
optic nerve. The optic nerve is very long in some 
species, owing to the vast width of the head.” 
In the sperm whale examined by Dr. Alderson “ the 
i 
