418 NERVOUS SYSTEM. 



ligament, the internal face of the choroid coat forms a conside- 

 rable number of radiated folds or little ridges, which converge 

 from behind forwards and inwards. These folds commence by 

 strise, almost imperceptible to the naked eye, which are in con- 

 tact with the fore part of the vitreous humour, and with the ca- 

 nal of Petit, and thereby not only impress the neighbouring por- 

 tion of the tunica hyaloidea with their shape, but even leave 

 upon it the black pigment with which they themselves are co- 

 vered. These folds, when. they get near the circumference of 

 the iris, coalesce one with another, and terminate in a conside- 

 rable number (from fifty to sixty, according to So3mmering,) of 

 processes, (Processus Ciliares,} the central extremities of which 

 are loose, and float in the aqueous humour. Some of these pro- 

 cesses are longer than others. As a whole, the ciliary processes 

 constitute a ring of radiating filaments, which are a line or more 

 in length, placed along side of, and in contact with, one another; 

 the external periphery of the ring adheres to the ciliary liga- 

 ment, and through it to the greater circumference of the iris, so 

 that the ring appears, but fallaciously, to be continuous with the 

 iris. In certain animals, as the sheep, the radiated appearance 

 of the iris, on its posterior face, favours this notion still more. 

 The internal periphery of the ring presents the central ends of 

 the filaments detached from one another, and of a downy ap- 

 pearance; with the handle of a knife they may be readily pushed 

 backwards and forwards. Generally speaking, the ciliary pro- 

 cesses are so much concealed by the iris, that they cannot be 

 seen in the living body through the cornea: in cases, however, 

 of extreme dilatation of the pupil by narcotic applications, their 

 central extremities are brought into view. 



The choroid coat always appears, when uninjected, of a very 

 dark brown or black colour, arising from a black paint (Pig- 

 mentum Nigrtan) being very thickly spread over the whole of 

 that surface of it which is adjacent to the retina, and being 

 also diffused through its thickness. This paint is more abun- 

 dant near the iris than posteriorly, being laid on there in flakes, 

 in the intervals between the ciliary striae, and tinging also the 

 ciliary processes. It may be removed in a considerable degree, 

 indeed almost entirely, by maceration, or by careful washing 

 with a camel's-hair pencil. It is supposed to be an exhalation 



