6 
to a vertical slit, probably when the animal accommodates for a near 
object. 
It must be confessed that not much is known about the size and 
shape of the avian pupil in the several conditions of accommoda¬ 
tion, convergence, illumination, etc. In the London “Zoo” I spent 
considerable time trying to decide the extent to which the pupils 
of night birds are affected by light. There is no doubt but that the 
owl’s pupils contract and expand in the presence and absence of 
light much as ours do. Flashing light into the eyes of all the owls 
had the same effect—an almost instant contraction of the pupil. 
Moreover, I was also able to determine a consensual contraction to 
light in several different species of owls. There are manifest diffi¬ 
culties in the way of exactly determining the effect of light upon 
birds’ pupils, as it is almost impossible in most instances to elimin¬ 
ate the effect upon the pupil of accommodative efforts—a factor 
that probably exerts no little influence'upon their size and shape. 
The Anie?'ior Chamber in birds is generally deep and the quan¬ 
tity of aqueous humor correspondingly large. The wide space 
between cornea and lens permits of greater antero-posterior move¬ 
ments of the crystalline in realizing the wide accommodative range 
needed by the bird in its frequent and extensive change of focus. 
Incidentally, also, it contributes to the peculiar brilliancy of the 
avian eye. 
The Ligamentum Pectinatum is an elaborate and extensive 
organ in the eyes of birds. According to Collins, 3 it arises at the 
limbus corneae a little in front of the root of the iris and extends 
backward between the striated muscle of Crampton and that part 
of the ciliary body attached to the ciliary processes. 
The Canal of Schlemm is proportionately large, and in sections 
of the bird’s eye is easily seen standing wide open. The presence 
of so capacious a lymph channel undoubtedly corroborates the view 
that the interior of the bird’s eye is the scene of great nutritional 
activity, requiring a drainage canal capable of carrying off waste 
products in considerable amounts from organs constantly func¬ 
tionating. 
The Ciliary Body of Birds , although well developed, is not, like 
that organ in man and most other animals, the only source of the 
3. E. Treacher Collins : The Lancet Feb. 24, 1900. 
