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The eye of the cave rat is, if anything, larger in proportion to its body 
weight than that of our gray rat (Figs. 3 and 4). The lens is in each case 
enormously large in proportion to the eye, so large, in fact, that very little 
space is left for the aqueous and vitreous humors. The pupil is capable 
of very wide dilation, as is true with most nocturnal animals. 
Fig. 4. Common Gray Rat (x 8). 
A. Aqueous Chamber. 
C. Choroid and Pigment Layers. 
L. Lens. 
R. Retina. 
S. Seclerotic. 
V. Vitreous Chamber. 
The head of the cave rat, being more rounded and less pointed than 
that of the gray rat, permits of a slightly deeper eye-socket. However, 
these two rats resemble each other in their ‘pop-eyed”’ appearance when 
frightened. 
A microscopical comparison of the retina also shows little difference. 
Bits of retina from corresponding parts of the eye of a cave rat and a 
gray rat were hardened by the same process, sectioned the same thickness 
and stained alike, so that the sections are directly comparable. Tig. 5 
represents semi-diagrammatic camera drawings of two such sections. 
