CHAP. XVII.] 



THE CILIARY MUSCLE. 



27 



Fig 116 



ob 



iris firmly to the sclerotic. The plexiform tissue of the posterior 

 elastic lamina of the cornea already noticed, adjoins this ligament, 

 and partially blends with it. 



The ciliary muscle is that grayish, semi-transparent structure 

 behind the ciliary ligament, and covering the outside of the ciliary 

 body. It has been described as muscular by many of the older 

 anatomists, especially by Porterfield, while 

 others have assigned to it a different cha- 

 racter. Lately it has been so regarded by 

 Wagner and Dr. Wallace of New York, 

 and we believe correctly. It belongs to the 

 unstriped variety of muscle, and its fibres 

 appear to radiate backwards from the junc- 

 tion of the sclerotic and cornea, and to lose 

 themselves on the outer surface of the 

 ciliary body. The more superficial fibres 

 are in contact with, but scarcely adhere 

 to, the sclerotic, and are inserted into 

 the posterior part of the ciliary body; 

 while the deeper ones seem to dip behind 



fhp iri trv fhp rnnrA nvrrmrmnf -ncjT-fa nf flio radiates, e. Iris. n. Lens, connected 



tne iris to tne more prominent parts 01 tne with the ciliaiy processes by the an- 



pilinrv nrnpp<a=jp<a whiph aTmrnnrTi fho leme terior wall of the canal of Petit, the 



Binary processes wmcn approacn tne lens, situation of which is marked by the*. 

 The ciliary muscle must have the effect -Magnified 3 diameters. 

 of advancing the ciliary processes, and with them the lens, towards 

 the cornea. The ciliary nerves pierce this muscle on their way to 

 the iris, distributing to it many filaments which may be seen for 

 the most part to cross the fibres. 



The muscular nature of this structure is confirmed by its anatomy in birds, 

 where it is largely developed, as noticed by Sir P. Crampton. We find its 

 fibres to be of the striped variety, like the circular fibres of the iris in the 

 same class, and to be supplied by ciliary nerves traversing the muscle in a 

 circular direction. They likewise all radiate from the cornea, at the circum- 

 ference of which they are attached to the deeper layers of the cornea proper, 

 the elastic lamina being here exceedingly thin. 



Within the choroid is the retina, which we shall describe as a 

 structure distinct from the optic nerve, though continuous with it; 

 reserving our account of that nerve, and of the others pertaining to 

 the eye, till the anatomy of the globe is concluded. 

 The retina is the sheet of nervous matter which receives the 

 images of external objects thrown upon it by the transparent media, 

 and it is accordingly placed immediately behind the vitreous hu- 



