. On the anatomy of vertebrates [electronic resource] . bur-rowers : they acquire the largest absolute and proportional size inthe Ruminant order. In no Mammal is bone developed in the sclerotic: in most a special ca- 193 • • vity, called e orbit, is fashionedin the facial part of the skull togive lodgment to the sees least indication of itin the blind cpiadrupeds abovenoted and in the ant-eaters : itis deepest, best defined, andmost completely walled in Man. In all Mammals with the eyedeveloped for sight, properlyso called, we recognise, as in thediagrammatic section, fig. 193,th
. On the anatomy of vertebrates [electronic resource] . bur-rowers : they acquire the largest absolute and proportional size inthe Ruminant order. In no Mammal is bone developed in the sclerotic: in most a special ca- 193 • • vity, called e orbit, is fashionedin the facial part of the skull togive lodgment to the sees least indication of itin the blind cpiadrupeds abovenoted and in the ant-eaters : itis deepest, best defined, andmost completely walled in Man. In all Mammals with the eyedeveloped for sight, properlyso called, we recognise, as in thediagrammatic section, fig. 193,the fibrous capsule, a, called6 sclerotic coat, the transparentfore part, b, called f cornea ; the vascular tunic, c, called choroidcoat, becoming thickened, at d, by the so-called ( ciliary ligament,from which the ciliary processes are, as it were, reflected back-ward upon the capsule of the lens,/: while the movable curtain,or 4 iris, is continued onward into the space between b and f,leaving a central opening, called (pupil, for the admission of. Diagrammatic section of Mammalian eye. cv OKGAN OF SIGHT IN MAMMALIA. 247 light. The choroid, c, is lined by the expansion of the optic nervecalled retina, which extends to the ciliary processes, and iskept outstretched by the £ vitreous humour contained in thecells of the delicate membrane called hyaloid, which restrainsits forward advance beyond the ( crystalline humour or lens,/*.The space in front of this body is occupied by the 4 aqueoushumour, and is divided by the iris into an i anterior and pos-terior chamber. The rays of light admitted by the cornea and pupil areslightly refracted in traversing the aqueous humour, and are sub-ject to a greater degree of convergence in passing through the 194 (A 7 fit V Diagram of course of luminous rays in traversing the humours of the eye. denser lens, fig. 194; when, striking the retina at the back ofthe globe, they there depict the image of the visual object, in-verted. In crepuscular
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