140 REPORT—1858. 
do they appear to be larger or smaller. The eye of the infant is larger, in propor- 
tion to the size of the body, than that of the adult; but it is by no means certain 
that the eye of the male is larger proportionately to the size of the body than the 
eye of the female. By some anatomists the human eye is described as a spheroid, 
the diameter of which, from before to behind, is greater than in any other direction. 
He had measured a great number of eyes, of the human subject as well as of animals ; 
and he found that, wherever there was a departure from the spherical figure, it was 
in the direction contrary to that which had been commonly stated. In some in- 
stances the difference between the two diameters was scarcely perceptible; in all, 
where a distinction was observed, the transverse was the greatest. He had pre- 
pared a set of tables (which were printed), containing the result of the measurement 
of 200 eyes of various creatures. In conclusion, Mr. Nunneley said—‘ The measure- 
ments, I think, clearly prove that whatever part the fibres of the optic nerve play in 
the phenomena of vision,—and they, in all probability, only convey to the sensorium 
the impression received by the true retinal elements,—the greatest number of them 
are distributed on that part of the eyeball where there is the greatest range of vision, 
and that the largest expanse of retina is on that part of the ball opposite to where 
objects are placed, and consequently it is where the visual images of them must fall. 
Thus the extent of vision is always in conformity with the space of retina on that 
side of the optic nerve; and as the rods and cellules appear always to correspond in 
abundance with the fibres, that side of the retina which receives the greatest number 
of images is most exercised ; or where the range of vision is the greatest, is always 
the largest. That this is a fact I think a careful comparison of the position of the 
eyes in the head, the size of the eyeball, and the exact position of the entrance of 
the nerve into it, with the mode of life and habits of various creatures, will render 
more obvious than a casual glance would do. To mention only a few instances as 
illustrations :—Man, from the erect position of his body, the horizontal placing of 
his eyes, and his habits, has a more panoptic range than any other creature (of 
course in this consideration all motions of the head, neck, and body of the animal 
must be excluded, and those of the eyeballs alone admitted). In him the optic nerve 
enters the ball not far from the centre, leaving, however, a somewhat shorter space 
on the inner and lower parts of the retina than on the upper and outer. Now, while 
man enjoys a free range of vision above the horizontal line, there are far more occa- 
sions for him to look at objects below than above this line, and thus mere visual 
images are projected to the upper and outer sides of the entrance of the optic nerve 
oftener than to the inner and lower sides of this spot. In the pig, who sees at no 
great range before him, and who seeks his food with the snout almost always in the 
ground, whose head and eyes are consequently for the most part downwards and 
near to the ground, the nerve enters the ball more outwardly and much lower than 
it does in man. The pig wants not to see far before him, but he does require while 
grubbing to look behind him, from whence danger comes. So with the timid herbi- 
vorous animals; look at the entrance of the nerve in the bullock and sheep, who 
pass so much time with the head in a dependent position near to the ground with 
the eye directed upon the surface, in open plains, where danger usually comes from 
behind; in them the upper and inner sides of the retina are much larger than the 
lower and outer portions, while in the deer who live in more wooded places, where 
danger is also from the front, but who, like the bullock, has the head downwards in 
feeding, though the inner or anterior side of the retina is still larger than the pos- 
terior, it is so to a much less extent than it is in the bullock—while the upper por- 
tion still continues as proportionately large as it is in sheep and bullocks. On the 
contrary, in the horse, who is not so preyed upon, who carries the head erect, and 
observes all around, the nerve enters the eye more nearly in the axis. In birds, 
with few exceptions, the upper portion of the retina is much more considerable than 
the lower parts, but the anterior and posterior portions vary much in different genera. 
Those whose locomotion is performed principally by the feet, and whose range of 
habitation is very small, as the common fowl and turkey, have the inner or anterior 
portion very considerably greater than the outer or posterior. Those birds whose 
range is greater and who use the wings for progression, but do not wander very far, 
as the grouse and partridge, have much less difference in the two portions of the 
retina; while in those birds whose flight is far and prolonged, as the crow, rook, 
