THE BALL OF THE EYE. 423 



Long Ciliary Arteries having gained the greater circumference 

 of the iris, bifurcates; the bifurcation runs along this circumfe- 

 rence, meets, and joins with the corresponding one of the other 

 arterial trunk. From the circle thus formed there proceed ra- 

 diated branches, that run towards the pupil, and form a/ound 

 its margin, by their frequent anastomoses, a fine vascular net- 

 work. The radiated branches themselves give off collateral 

 branches, which supply the intermediate spaces of the iris.* 

 The veins of the iris are also numerous, but cannot be quite so 

 distinctly seen: they enter into the long ciliary veins, and also 

 into the vasa vortieosa. 



The nerves of the Iris belong, in part, also to the choroid 

 coat, and are classed under the term Ciliary, (JVerra Ciliares.) 

 They arise from the ophthalmic ganglion, and from the trunks 

 contributing thereto, and are about twenty in number. They 

 penetrate the posterior part of the sclerotica obliquely, and 

 then run forwards between it and the choroides. Having 

 reached the posterior part of the ciliary ligament, they pene- 

 trate it, and distribute their filaments in its substance, after the 

 same fashion that the trigeminus nerve is divided m its gan- 

 glion. This circumstance has given occasion to Simmering 

 to consider the ligament as a true ganglion, and to call it An- 

 nulus Gangliformis. The nerves then get to the front of the 

 iris, and are there distributed as white radiating filaments; in 

 the course of which may be observed small nodes, supposed by 

 Meckel to be Ganglions* 



The trunks of the ciliary nerves depart from the common 

 form of such bodies, by being flattened instead of cylindrical: 

 they are small, and resemble sewing threads. From their num- 

 ber, the iris is probably more abundantly supplied with nerves 

 than any other organ of the bodj^ 



The Retina forms the third coat of the eye, and lines the in- 

 ternal face of the choroides almost in its whole extent. The 

 optic nerve having passed through the sclerotica, terminates on 

 its inner side by a bulb or button-like end, from the circumfe- 

 rence of which the retina begins to expand, and maybe traced 

 satisfactorily as far as the commencement of the ciliary plaits of 

 the choroid coat, where it terminates by a straight edge, some- 



* Soemmcring, Iconcs Oculi Humani. 



