1524 



A MANUAL OF ANATOMY 



interna and membrana limitans externa are sometimes counted as 

 layers of the retina, under which circumstances the retinal layers 

 would be ien in number, instead of eight, as stated). From the 

 membrana limitans externa delicate offsets enter the layer of rods 

 and cones, in the innermost part of which they form fibre-baskets in 

 connection with the deep ends of the rods and cones. As the sus- 

 tentacular fibres pass through the inner nuclear layer each presents an 

 oval nucleus, which contains a nucleolus. This nucleus is variously 

 described as being situated on one side of the fibre, or as involving 

 its whole circumference. Throughout their course the sustentacular 



Membrana Limitans 

 Externa 



Outer Molecular^, 

 Layer 



Nucleus of one of— — 

 Miiller's Fibres 



Inner Molecular 

 Layer 



Muller's Fibres 

 Limitans Interna. 

 Membrana 



Rods and Cones 



Outer Nuclear 

 Layer 



Subepithelial 

 Ganglion-cell 



Stellate Ganglion- 

 cell 



_ Bipolar Ganglion 



Gai 

 ell 



Centrifugal Nerve-fibre 



- Multipolar 

 Ganglion-cell 



Multipolar 

 Gangliou-cell 

 ^ Layer of Nerve- 

 "" fibres 



Fig. 637. — Diagram of the Elements of the Retina (Wiedersheim, 

 AFTER Ph. St6hr). 



A, Nervous Elements ; B, Supporting Elements. 



fibres give off lateral offsets, which increase in number from within 

 outwards. 



Structure of the Macula Lutea and Fovea Centralis.— The chief 

 structural characters of the macula lutea and fovea centralis may 

 be stated in the following tabular manner : 



Macula Lutea. 



1. Cones only. 



2. Outer nuclear layer has only cone- 



fibres, disposed obliquely. 



3. Ganglionic ayer very thick, cells 



being several layers deep. 



4. Stratum opticum not continuously 



disposed. 



Fovea Centralis. 



1. Thinnest part of the retina. 



2. Pigmentary layer thick. 



3. Cones only. 



4. Outer nuclear layer has only 



cone-libres. 



5. Ganglionic layer absent. 



6. Stratum opticum absent. 



