300 ELEMENTS OF HISTOLOGY. [Chap, xxxvn. 



(Schwalbe) as a lymphatic canal; by others (Leber) 

 as a venous vessel. 



418. IV. The ciliary muscle (Fig. 152) or 

 tensor choroidese, is fixed to this ligamentum pecti- 

 natum ; it is composed of bundles of non-striped 

 muscular tissue. This muscle consists of two parts : 

 (a) one of circular bundles nearest to the iris this 

 is the portio Miilleri ; (b) the greater part is composed 

 of radiating bundles, passing from the ligamentum 

 pectinatum in a meridional direction for a consider- 

 able distance backwards into the tissue of the choroid 

 membrane. It occupies the space between the liga- 

 mentum pectinatum, sclerotic, ciliary processes, and 

 the adjoining portion of the choroid membrane. 

 The bundles of the muscle are arranged more 

 or less in lamellae; within each lamella they form 

 plexuses. 



A rich plexus of non-medullated nerve-fibres, with 

 groups of ganglion cells, belongs to the ciliary muscle. 



CHAPTER XXXVII. 



THE IRIS, CILIARY PROCESSES, AND CHOROID. 



419. I. THE iris consists of the following layers : 



(1) The endothelium of the anterior surface : trans- 

 parent, flattened, or polyhedral cells, each with a 

 spherical or slightly oval nucleus ; in dark-coloured 

 eyes of man and mammals brown pigment granules 

 are contained in the cell-substance. 



(2) A delicate hyaline basement membrane : it is 

 continuous through the trabeculse of the ligamentum 

 pectinatum, with the membrana Descemeti of the 

 cornea. 



