THE BALL OP THE EYE. 417 



repeated observations on the practice of Dr. Physick, as well as 

 in instances in my own hands. 



The Choroid Coat (Tunica Choroidea, Fasculosa,) is placed 

 immediately within the circumference of the sclerotica, an*J is 

 of equal extent. At its posterior part it furnishes, for the pas- 

 sage of the optic nerve, a single annular opening, the margin of 

 which is somewhat thickened, and perfectly distinct from the 

 pia mater investment of the nerve, from which some anatomists 

 have desired to trace this coat. The anterior opening of the 

 choroid is bounded by the ciliary ligament and by the iris. On 

 its outer side may be seen an abundance of loose flocculent cellu- 

 lar substance which joins it to the sclerotica. Internally, it is 

 spread over the retina, but does not adhere to it. 



The choroid coat is closely fastened, at its anterior margin, to 

 the corresponding part of the sclerotica, by a ring which sur- 

 rounds it, of a short compact cellular tissue. This ring, called 

 the Ciliary Ligament, (Ligamentum Ciliare, Orbiculus Ciliaris^ 

 is from a line to two lines in breadth, and may be readily dis- 

 tinguished by its whiteness, contrasted with the dark colour of 

 the choroid. It is intimately united to the latter, and seems to 

 form a part of its structure, whereby it is caused to detach itself 

 entirely from the sclerotica, and to adhere, by preference, to the 

 choroid when these two membranes are separated.* The iris is 

 set in the front margin of the ciliary ligament, so that the scle- 

 rotica and the cornea may be peeled from the choroidea and iris, 

 without impairing the continuity of the two latter. Just beyond 

 the junction of the two last, the ligament presents a small ridge 

 or elevation all around, which is fitted into a corresponding fossa 

 at the circumference of the posterior face of the cornea. 



The internal face of the choroid coat, as well as its anterior 

 margin, undergo a very remarkable change from the general 

 plan of this tunic, by forming what is called the Ciliary Body, 

 (Corpus Ciliare, Corona Ciliaris.) In order to see this in the 

 most favourable manner, the eye should be laid on the cornea, 

 and its posterior half cut away. It will then be evident, that 

 just behind the iris, and within the circumference of the ciliary 



* Fontana asserted that a circular canal was to be found in this ligament ; 

 many examiners have failed in finding it, and its existence is denied. 



