174 OEGANS OF SENSE. 



by a layer of pigment cells, but these are regular 

 polygons, more numerous, and containing a larger 

 quantity of pigment, than those last mentioned (PL 

 II. fig. I.) ; this layer has no connexion with the 

 retina, with which it is in contact. Between these 

 two layers of pigment cells is the proper substance of 

 the choroid membrane. 



cmary muscles. The greyish thickened ring of tissue which forms 

 the limit, anteriorly, of the choroid, and by which it 

 is firmly united to the sclerotica, is muscular in its 

 nature, and constitutes the principal bulk, or body, of 

 the ciliary muscle ; it is also described as the ciliary 

 circle or ring, ciliary ligament, and ciliary ganglion. 

 On its surface it appears to consist of non-striated 

 muscular fibres, parallel in their direction with the 

 antero-posterior axis of the globe of the eye. Ante- 

 riorly it grows thin (jVd of a line in thickness), and 

 is inserted, at first, into the inferior wall of the canal 

 of Schlemm, and, a little farther on, into the posterior 

 extremity of a fasciculus of fibres which is continuous 

 with the amorphous border of the cornea, and adhe- 

 rent also to the circumference of the iris, called the 

 pectiniform ligament (PL XXVIII. fig. IV. 3). The 

 deeper portions of the ciliary muscle, which are in 

 relation with the ciliary processes, consist of inter- 

 laced muscular fibres; at. least this is the inference to 

 be drawn from the variable aspect presented by the 

 muscular nuclei of the part in a section (fig. IV. 5, 6). 

 Posteriorly, the muscle gives off longitudinal fasciculi 

 which extend as far as the middle of the choroid, and 

 anteriorly, it presents similar fasciculi of fibres which 

 penetrate the iris, and converge towards the pupil. 



