HISTOLOGICAL ELEMENTS RETINA NECTURUS 439 
11. Nuclei of Miiller’s fibers lie chiefly in the inner nuclear 
layer, but a small number may be found in the outer nuclear layer. 
In an average sized retina there are about 26,734 of these nuclei, 
the maximum and minimum numbers being 33,000 and 22,000, 
respectively. 
12. The number of ganglion cells in the smallest retina meas- 
ured, was 24,758; in the largest, 37,229; and in an average-sized 
retina 30,464. 
13. The optic nerve of Necturus varies in diameter with the 
plane of transection. Near the chiasma its cross section has 
on the average an area of 0.0085 sq. mm., and an average of 962 
nerve fibers; near the eyeball the average area of the cross section 
is 0.0216 sq. mm., with an average of 1982 nerve fibers. 
14. The proportion of histological elements of the retina and 
optic nerve are approximately as follows: visual cells 111, nuclei 
in the outer nuclear layer 121, nuclei in the inner nuclear layer, 
exclusive of Miiller’s fibers, 175, ganglion-cell nuclei 30, Miiller’s 
fibers 26, optic nerve fibers distally 2, optic nerve fibers proxi- 
mally 1. 
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