HISTOLOGICAL ELEMENTS RETINA NECTURUS 425 
layer thick, are larger, more rounded and less closely grouped 
than are the nuclei of the other retinal layers. Sections from 
the five visual regions (table 10) in five retinas show as before a 
slight variation in the average number of nuclei per unit area, 
but this I believe is due to accidental conditions and is not at 
all consequential. Contrary to the condition found in the outer 
nuclear layer, the number of nuclei in the ganglionic layer is 
greater in the fundus than elsewhere. In table 11 the average 
number of nuclei per area of 0.39 sq. mm. is given as 111.1 
and the total number of nuclei in a retina of average size is 
about 30,000. 
' Thus we see that in passing centripetally through the layers 
of the retina there is a gradual decrease in the number of elements 
composing each layer, except in the inner nuclear layer, so that 
according to the views usually expressed, visual impulses aris- 
ing in a number of visual cells are transmitted to the central 
organ over a greatly reduced number of elements. 
d. Miiller’s fibers. Miiller’s fibers were counted to best advan- 
tage in tangential sections through the inner reticular layer close 
to the ganglion-cell layer, where they appeared as intensely red 
spots in a net-work of small light-red fibers. They occurred in 
pairs and triplets as well as singly (figs. 1 to 4). I have assumed 
that each fiber represents a cell with a nucleus lying generally 
in the inner nuclear layer. Slight variations in the number of 
TABLE 9 
Total numbers of nuclei of the outer nuclear layer in retinas of minimum, maximum, 
and average sizes 
& y 4 | 4 
Sues 2 6 3 < z 
in< < 
apa < a z mee & & We mare we oe 
| a oI % ic] 
sede | Oo EE a 2a oF OB Cea 
|G Ros | <n Pa 2 fo af gb, 
ZA = 5 tal Z 
7h | Ba. 52 Sak ag ad Hos 
RELATIVE SIZE (QQ AB 3 | gas ae baa as | Bz Ae 
OF EYEBALLS Bas, | ae on es ae aia eee 
lasca <m Zak ae | oAae 7Ae ZAe ZA8A 
i44aze cop | A | SAE Ene aa | eae) 
pbatge ee a3 | Sox Ho Hoe HOO 
\/PBA& <4 Ap | @e@e@a& | a 
OR Hg a aga stir gee <aBm =D <pp 
\dmesaaao ap & Zan RZan Aza AAG 
4 fe p > re) ° ° 
1S) | < Zz < & & & 
‘ ate z 
75,840 21,764 | 97,604 
Minimum.... | 10.8184 | 0.039 | 277.394] 273. 
15.177 2 106,400 30,558 | 136,958 
Maximum... .| (a OFO39 Wr asOr lee 
Average of 14 
retinas.....| 18.4698 | 0.039 | 345.379 | 273.4 94,427 27,097 | 121,524 
