CHOROID COAT. 793 



into processes (pillars of the iris or ligament-urn pectinatum iridis) 

 which are partly reflected on to the front of the iris, and partly join 

 the sclerotic and choroid coats. 



In the healthy condition the blood-vessels do not permeate the no vessels; 

 cornea, but cease in capillary loops at the circumference. Numerous many 

 tine branches of the ciliary nerves ramify in its substance. 



VASCULAR COAT OF THE EYEBALL (fig. 289). The next cover- Vascular 

 ing is situate within the sclerotic, and is formed in large part of f" r d c ^at! CU 

 blood- vessels ; the muscles of the interior of the ball also belong 

 to this coat. 



It is constructed of three parts, a posterior (choroid) correspond- Compo- 

 ing with the sclerotic, an anterior (iris) opposite the cornea, and an lie 

 intermediate ring (ciliary muscle) on a level with the union of the 

 sclerotic and cornea. 



Dissection. Supposing the cornea of an eye cut through circularly Dissection 

 as before directed, it will be necessary to take away the sclerotic to c^o^id 116 

 lay bare the choroid coat. With the point of the scalpel or with portion, 

 a shut scissors, detach the fore part of the sclerotic from the front 

 of the choroid by breaking through a soft w r hitish structure uniting 

 them. Then, the eye being put into water, the outer coat is to be 

 removed by cutting it away piecemeal with the scissors ; in taking 

 it off, the slender vessels and nerves beneath are to be preserved. 

 The white ring round the eye in front, which comes into view 

 during the dissection, is the ciliary muscle. 



For the purpose of obtaining a front view of the ciliary pro- TO show 

 cesses, which are connected with the anterior termination of the 

 choroid coat, let the cornea be removed as before on another eyeball. 

 Detach next the fore part of the sclerotic from the choroid ; and 

 after three or four cuts have been made in it towards the optic 

 nerve, the resulting flaps may be pinned out, so as to support the 

 eye in an upright position (fig. 289). On removing with care the by an 

 iris, taking it away from the centre towards the circumference, the antenor 

 ciliary processes beneath will be displayed. A posterior view of andapos- 

 the processes may be prepared on another ball by cutting through tenor view> 

 it circularly with scissors, about one-third of an inch behind the 

 cornea, so that the anterior can be removed from the posterior half ; 

 on taking away the portion of the vitreous mass adherent to the 

 anterior part of the ball, and washing off the pigment from the 

 back of the iris, the small processes will be made manifest. By 

 means of the last dissection the interior of the choroid coat may 

 be seen. 



If a vertical sagittal section is made of another eyeball (fig. 290), To make a 

 it will show the ciliary processes in their natural position, and will ^rtion 1 

 demonstrate the relative situation of all the parts. This section, 

 which is made with difficulty, should be attempted in water with 

 a large sharp knife, and on a surface of wax or wood, after the 

 cornea and sclerotic have been cut with scissors. When the eye 

 has been divided, the halves should remain in water. 



The CHOROID COAT (fig. 288, 6) is a thin membrane of a dark Choroid: 

 colour, and extends from the optic nerve to the fore part of the extent ; 



