THE PLACENTALIAN EYE 



683 



muscle are delegated to the anterior surface of the lens, which exhibits 

 the most elastic deformation. Other fibers, the perpendicular ones, seem 

 to have been oriented favorably to serve as check ligaments, keeping 

 minimal the change in curvature of the posterior surface of the lens. 



The lens is nowhere so flat as in man and other diurnal primates. 

 It is perfectly spherical only in seals and in some toothed whales; but it 



Fig. 197 — The ciliary region in placental mammals. 



a, portion of anterior segment of a carnivore, Felts lybtca. Redrawn, modified, from Franz. 

 c- cornea; cp- ciliary process; /'- iris; /- limbus corneae; ot- ora terminalis retinje; pi- p>ectin- 

 ate ligament (three fibers show); s- sclera; sr- sensory retina. 



b, diagrammatic thick frontal section in a carnivore (cat), showing paired bundles of zonule 

 fibers against the faces of the major ciliary processes, and the smaller 'perpendicular' bundles 

 associated with the minor processes. Based upon a photomicrograph of Kahmann. 



c, carnivore (cat); d, ungulate (pig); e, primate (man). Combined from figures of Kah- 

 mann. Dotted line shows profile of major ciliary process. 



<•- cornea; i- iris; /- lens; p- perpendicular fans (see text); s- sclera. 



