i-:x.\Mi.\.\T/<>.\ 



i-:\i-:it.\LL 



already been described. Its posterior surface exhibits numerous radial folds run- 

 ning from the ciliary processes to near the pupillary border; a thick layer of black 

 pigment covers it. and curls around its inner edge, so as to come into vie\\ all around 

 the pupil as seen from in front. The jH-riphcral or ciliary border of the iris is con- 

 tinuous with the front of the ciliary body, \\here it also receives fibres from the 

 ligamentum |>ectinatuin iridis; in otiiei resects the iris is quite free, merely resting 

 on the front of the lens-capsule near the pupil. Its slroma is spongy in character, 

 being made up of vessels covered by a thick advent it in, running from the |>eriphery 

 to the pupillary border, with interspaces iilled by branching pigment cells, which 

 are particularly abundant near the front surface. Deep in the stroma. running 

 around near the pupillary border, we find a broad Hat band of smooth muscle-lib 

 constituting the sphincter pupillae or sphincter iridis. Immediately behind the 



Fio. 727. DIAGRAMMATIC HORIZONTAL SECTION or EYEBALL AND ORBIT. 



i A ft IT Fuchs, much modified.) 



Periorbita green; muscle-fascia red; Tenon's capsule yellow. 



Lower lachrymal puncttim 

 Conita 



Opening of Meibomian gland 



Caninrle 



Inner palpebral ligament 



Anterior clin<i<< < 



li (I 



Corona ciliaris 



rhifului ciliaris 



,;,l if :n, 

 vena i 



Outer check ligament 



' rrntralis retinte 



HuBCle-fascia 



Orbital blood-vessel 



Central retinal vessels in 

 optic nerve 



External rectua muscle 



. NASAL PROCESS OF 



UPPER JAW 

 Anterior limb of 

 inner palpebral 

 ligament 

 Lachrymal sac 



Posterior limb of inner 

 palpebral ligament 

 with Horner'a muacle 

 apringing from it 



LACHRYMAL BONE 



Proceas of muacle-faa- 



cla to under aurface of 



conjunctiva 



Ora sei't'tit" 



Tendon of insertion of 

 Internal rectui 



Inner check ligament 



Periorbita 



ORBITAL PLATE OF ETHMOID 

 BONE 



Posterior lamina of 

 muecle-faacta lined 

 by Teuon'a capsule 



Internal rectua muacle 



OPTIC KKRVE 



vascular tissue lies a thin membrane, consisting of fine, straight fibres running 

 radially from the ciliary border to just behind the sphincter. The nature of these 

 fibres was long in dispute, but they are now accepted as being undoubtedly smooth 

 muscular the dilator pupillae. 



The sphincter pupill.T and the ciliary muscle are supplied by the third nerve by 

 way of the ciliary ganglion. The dilator pupillae is supplied by sympathetic fibres, 

 which have their origin from the cells of the superior cervical ganglion. Thence they 

 ascend in the carotid and cavernous plexuses, and join the ophthalmic division of 

 the fifth nerve, passing to the eyeball by way of the long ciliary nerves. The white 

 rami fibres associated with these fibres leave the spinal cord by the motor roots of 

 the first two or three thoracic nerves, and ascend the sympathetic trunk to the 

 superior cervical ganglion without interruption. 



Posteriorly the iris is lined by the pigment already mentioned, which really 



