THE EYE 93 



a. The sclerotic consLsts chiefly of hyaline cartilage. 



b. The choroid is a vascular plexus, with much pigment. 



c. The retina is composed of the following layers from 



without inwards : 



i. A layer of pigment cells, sending processes between 

 the rods and cones. 



ii. The rods and cones are a layer of columnar bodies 

 placed vertically to the surface : the rods are 

 far more numerous, and much larger than the 

 cones : each consists of an inner and an outer 

 segment. 



iii. The outer limiting membrane is seen in sections 

 as an exceedingly thin line separating the rods 

 and cones from the outer nuclear layer. 



iv. The outer nuclear layer is a moderately thick layer, 

 well stained, and very closely connected with the 

 rods and cones. 



v. The outer molecular layer is a very thin layer, 

 not stained : it is finely granular or reticular in 

 structure. 



vi. The inner nuclear layer is thick and well stained. 

 It consists of several layers of large nuclei, sur- 

 rounded by thin layers of protoplasm, produced 

 into radial processes, 

 vii. The inner molecular layer is a thick, finely granular 



layer, not stained, 

 viii. The layer of nucleated nerve cells (ganglion cells) 

 is a single layer of large branched cells. 



ix. The layer of nerve fibres is formed by the branches 

 of the optic nerve. 



X. The inner limiting membrane, formed by the cone- 

 shaped ends of Miiller's fibres. 



xi. The radial fibres, or Miiller's fibres, commence with 

 expanded ends in the layer of nerve fibres and 

 stretch outwards : they can easily be traced 

 through the inner molecular layer. They consist 

 of connective tissue and serve to strengthen and 

 support the retina, 



