THE CATS. I5 
younger the Cats the rarer the cases in which the pupil is 
round ; and, conversely, the older the Cats the greater the 
prevalence of round pupils. This, I think, may be due to a 
decrease of the elasticity and consequent contractility of the 
iris as the animals grow older. 
“In no case have I noticed any convergence of the eyes, or 
any contraction of the pupil in accommodation for near objects. 
Sudden bright illumination, however, invariably causes con- 
traction. 
“The Cat’s iris contracts in a very definite and curious way. 
It may be imitated most accurately by causing two discs to 
overlap, until the horizontal diameter is equal to half the ver- 
tical (acute oval), when the contraction ceases in the vertical 
direction, but continues horizontally until the sides meet, 
forming two parallel vertical lines in close contact. At the 
extremities of this vertical slit there are always two round pin- 
holes, which are caused by the inability of the fibres of the iris 
to come further together ; if examined with a strong magnify- 
ing-glass, the radiating fibres of the iris are seen surrounding 
these points. 
“When I held a Cat’s face so that the unobscured sun shone 
directly on the centre of the pupil, and its image could be seen 
on the cornea, I noticed the pupil immediately contract to the 
above-mentioned vertical slit. So close was the contact between 
the free margins of the iris that, so far as I could judge, no 
light entered the eye except through the two pinholes. In 
fact, I found I could hold a Cat with the lids held apart so 
that the sun shone directly on to the pupils, without it showing 
any sign of discomfort, nor did the animal trouble to use its 
nictitating membrane. In this respect it had the advantage 
over the big /é/ide with pupils that contract in a circular 
manner, since a circular pupil can never contract completely 
so long as it remains a circle,” 
