SIGHT. 561 



" The iris (whose posterior surface is lined by a brown pig- 

 ment, and termed uvea) lies anteriorly to the ciliary processes, 

 is flat, and washed on all sides by the aqueous humour ; narrower 

 towards the nose, broader towards the temples. Its texture is 

 dense and cellular, and contains no vestige of muscular fibre. 

 We must regard it, with Zinn m , as a membrane sui generis, and 

 not as a prolongation of the chorioid. The anterior surface is 

 -differently coloured in different persons, and, during life, has a 

 flocculent appearance. 



" The blood-vessels of the iris run chiefly on its anterior sur- 

 face, and in the foetus are continued into the membrana pupillaris , 

 which begins to open in its centre at the seventh or eighth month 

 of pregnancy, when the eyes have acquired some degree of size, 

 and when, probably, the elliptic arches of its vessels begin to be 

 gradually retracted into the inner ring of the iris, which ring I 

 have never been able to perceive distinctly before that period. 



" The posterior of the two circular membranes bears the 

 name of ligamentum or corpus ciliare ; and, inclining backwards, 

 lies at a distance from the iris. Its external edge is thick P and 

 adheres to the ciliary circle : the internal is thin, and, to- 

 gether with the adjacent zonula of Zinna, surrounds the margin 

 of the capsule of the lens. The brown pigment is copiously dif- 

 fused over it. 



" Its anterior surface, lying opposite to the uvea, is striated. 



" The posterior, lying upon the vitreous humour, is marked 

 by about seventy plicae, which are beautifully flocculent, and re- 

 markable for a set of indescribably minute and elegant blood- 



m " Comment. Soc. Sclent. Getting, t. iv. p. 199." 



n " On the remarkable mutual relation of the arteries and nerves of the internal 

 parts of the eye, and especially of the iris, see Diet. G. Kieser, De Anamorphosi 

 oculi. Getting. 1804. 4to." 



" This beautiful membrane was first discovered by Francis Sandys a cele- 

 brated maker of anatomical preparations : it was first described and exhibited in 

 an engraving by Ever. J. Wachendorf, Commerc. Utter. Nor. 1 740, hebd. 1.8." 



p " The ciliary canal, discovered by Fel. Fontana, (Sur le venin de la vipere, 

 vol. ii. tab. vii. fig. 8, 9, 10.) and afterwards described more accurately by 

 Adolp. Murray (Nov. act. Upsaliens. vol. iii.), runs, in bisulcous animals, along 

 this thick edge." 



q " Doellinger, Nov. Act. Ac. N. C. t. ix. p. 267. sqq. tab. vii. 



C. J. M. Langenbeck, Neue Bibl. fur die Chirurgie, iii. B. 1. St. tab. 1. 11." 



P P 2 



