26 



THE EYE. 



enhanced by a layer of iridescent endothelial cells, which becomes formed immediately within 

 the fibrous layer (Sattler). 



In the outer part of the coat are situated, as just stated, the larger branches of 

 the vessels. The arteries (short ciliary) are comparatively large and numerous, and 



Fig. 30. LATERAL VIEW OF THE ARTERIES OF THE CHOROID AND IRIS, (From Arnold.) 



a, optic nerve ; b, part of the sclerotic left behind ; c, region of ciliary muscle ; d, iris ; 1 , posterior 

 ciliary arteries piercing the sclerotic and passing along the choroid ; 2, one of the long ciliary arteries ; 

 3, anterior ciliary arteries. 



Fig. 31. LATERAL VIEW OF THE VEINS OF THE CHOROID. (From Arnold.) 



1, 1, two trunks of the venae vorticosse at the piace where they leave the choroid and pierce the 

 sclerotic coat. The other lettering as in fig. 30. 



piercing the sclerotic close to the optic nerve (figs. 30 and 32), divide into branches 

 which are directed at first forwards but soon bend obliquely inwards to end in the 

 capillary layer; whilst the veins external to the arteries are disposed in curves (vasa 



Fig. 32. INJECTED BLOOD-VESSELS OF 

 THE CHOROID COAT (from Sap- 

 pey). 30 diameters. 



1, one of the larger veins ; 2, 

 small communicating vessels ; 3, 

 branches dividing into the smallest 

 vessels. 



vorticosa) as they converge to 

 four or five principal trunks 

 (fig. 81, I,/; fig. 26), which 

 pierce the sclerotic about half 

 way between the margin of 

 the cornea and the entrance 

 of the optic nerve. In the 

 intervals between the vessels 

 are elongated and stellate pig- 

 ment-cells. The veins, like 

 those of the pia mater, have 

 no muscular tissue ; they are 

 enclosed by an adventitious sheath, between which and the endothelium, which 

 forms the wall of the vein, is a lymph-space (perivascular sheath). The arteries 

 have, besides the ordinary circular muscular fibres, strands of longitudinally 

 disposed plain muscular tissue in their adventitia. As the vense vorticosa3 pass 

 through the sclerotic they are ensheathed by a prolongation of suprachoroidal 

 tissue (Fuchs). 



