rv 
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intra-ocular fluids and the nutritive supply to the lens. As we 
shall later see, that peculiar organ, the pecten (the analogue of the 
falciform process of reptiles and some mammals) largely supple¬ 
ments the supply of nutritive fluid required by the intra-ocular tis¬ 
sues. 
The chief muscle of accommodation in birds is probably that 
known as Crampton's. While variations in the shape of the globu¬ 
lar lens of birds, under the influence of the ciliarv fibers, undoubt- 
s 
Fig. 1.—Cross section of the brain, orbits and eyebails of the Kinglet (Regulus 
satrapa), showing the various ocular structures and their relations, especially 
the deep right fovea, the pectens, etc. 
edlv result in increase of curvature and of refractive effect, vet the 
principal change in the direction of the light rays is produced by 
transforming a more or less round or ovoid globe into a tubular 
structure fitted with a conical lens. This alteration is brought about 
by the contraction of the circular muscle of Crampton—an intra¬ 
ocular band that encircles the bird's eye about the equator. The 
unyielding walls of the globe direct the pressure forward, the ciliary 
muscle relaxes, and the internal pressure pushes the crystalline 
into the anterior chamber. This movement is now assisted by the 
