576 BULBUS OCULI 



continuous with the iris internally, the sclera anteriorly, and 

 the corona ciliaris and the chorioid posteriorly. 



Ciliary Muscle. This is composed of involuntary muscular 

 tissue, but the arrangement of its fibres can be seen only 

 when thin sections of the eyeball are examined under the 

 microscope. It is then obvious that the fibres are disposed 

 in two groups, viz., a radiating and a circular. 



The radiating fibres arise from the deep aspect of the 

 sclera close to the margin of the cornea. From this 

 they radiate posteriorly, in a meridional direction, and gain 

 insertion into the chorioid coat in the region of the ciliary 

 processes. The circular fibres consist of two or three bundles 



Chorioid 



Chorioid (cut 

 edge of) 



Ciliary fold - L ,_ 



Ciliary process 



FIG. 254. Posterior view of Lens and Zonula Ciliaris. 

 (Professor Arthur Thomson. ) 



placed upon the deep aspect of the radiating portion of the 

 muscle. They form a muscular ring around the outer circum- 

 ference of the iris. 



Dissection. To obtain a view of the ciliary processes, a frontal section 

 should be made through an eyeball a short distance anterior to the 

 equator. The portion of the vitreous body which occupies the posterior 

 segment of the eyeball should be carefully removed. When this is done, 

 the deep aspect of the corona ciliaris will be seen. It is covered with 

 ciliary processes which radiate posteriorly from the circumference of the 

 crystalline lens. By washing out the pigment from this part of the vascular 

 tunic, the arrangement of the processes will be displayed more fully. 



A second dissection may be made in another eyeball with the object of 

 exposing the ciliary processes from the front. In this case remove the 

 cornea with the scissors by cutting round the corneo-scleral junction. The 

 iris is now brought conspicuously into view, and may, with advantage, be 

 studied at this stage. Several cuts in the meridional direction, and at 



