THE RETINA. 



123 



be estimated at over 3,000,000; and the rods at 

 30,000,000.* 



Fig. Y8.— Section through the retina (after Mas. Schultze). Beginning from the outside, 

 1, limitary membrane ; 2, layer of nerve-fibres ; 3. layer of nerve-cells; 4, nuclear 

 layer; 5, inner nuclear layer; 6, intermediate nuclear layer; 7, outer nuclear 

 layer ; 8, posterior membrane ; 9, layer of small rods and cones ; 10, choroid. 



* Sulzer estimates the cones at 3,360,000 ; Krause places the cones 

 at 7,000,000, the rods at 130,000,000 ; but Professor M. Foster tells me 

 that he thinks the latter figure is too higli. 



