70 



BULLETIN OF THE 



pigment layer extends on either side beyond the lens, its outer edge be- 

 coming on one side (the lower one in the figure) continuous with the 

 inner layer of pigment, and on the other side with the pigment layer of 

 the retina. The connection with the outer is shown rather indistinctly 

 in the section figured, but much more distinctly in some of the other 

 sections of the series, as is also the fact that at places the iris is entirely 

 cut off from the retinal pigment. If, then, these layers of pigment have 

 come neither from the lens nor the retina, the only other structures 

 in this region that they could come from are the vitreous body and the 

 hyaloid membrane. In other respects this eye does not differ appre- 

 ciably from the usual structure already described, with this exception, 

 that the undifferentiated layer of the retina shows somewhat less differ- 

 entiation than usual, I have studied these sections in vain to find 

 convincing evidence of actual degeneration within the retinal elements 

 themselves, in addition to the pigmentation. 



I now present a table showing some of the results of measurements 

 that have been made of the retina, lens, and optic nerve : — 



Entire retina (including pigment layer) . . . 



Pigment layer 



Nerve fibre layer 



Ganglion cell layer 



Inner reticular layer 



Undifferentiated layer 



" Undifferentiated layer " of Nos. 1, 2, and 3 : 



Outer nuclear layer 



Basal nuclei in outer nuclear layer . . . 



Inner nuclear layer (including outer retic- 

 ular layer) 



Outer reticular layer 



Tangential cell layer 



Inner nuclear layer 



Diameter of lens 



Thickness of optic nerve at entrance to retina 

 Length of rods 



Two Speci- 

 mens, each 

 IQnim. long. 



.095 



.055 



.0029 



.004 



.013 



.017 



.075 



.046 



.0014 



.0029 



.0058 



.001 



.205 



S<pec. 

 SOmm. 

 long. 



.110 



.063 



.0043 



.0072 



.0116 



.0203 



Spec. Spec. of 

 60mm. I Cleve- 

 long.i landia 



.145 



.078 



.0058 



.0058 



.018 



.0317 



.0058 

 .0029 



.002J 



.011 

 .032 



.136 



.042 



.05 



.05 



.021 



.016 

 .0029 



.0018 



.0029 



.029 



.784 



.117 



Perhaps the most important thing that these measurements reveal is 

 the fact that the eyes are subject to great variation, as well in the pro- 



1 The same specimen from which Figures 13 and 21 were drawn. 



