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The optic nerves will be described with the optic ganglion. 
The cortical and central cell groups. The cortex. With exceptions 
already noted, the medulla is covered with nerve cells. These cells 
are small laterally, both dorsally and ventrally, but large posteriorly, 
with processes directed anteriorly. There may be one or several 
layers of cells; they increase in number toward the posterior, dorsal 
and ventral surfaces. 
Anteriorly, they partly surround the giant cells laterally and 
merge into the group of small and medium-sized cells. 
The posterior large-cell group extends somewhat laterally and is 
split into two groups by the medulla and oesophageal nerves (Diagrams 3, 
4, 5, 6; Fig. 11, 12). These two groups are again split into two 
each, an anterior and posterior, by the appearance of the post-lateral 
medulla (Diagrams 7,8; Fig. 13, 14) and the anterior group is forced 
still farther forward. Many of the large cells can be traced for some 
distance in the commissures. 
Central small and medium-sized cell group. This collection of 
cells surrounds the giant cell group posteriorly and laterally. Dorso- 
laterally and ventro-laterally they can not be distinguished readily 
from the cortical cells (Diagrams 2, 3, 7, 8, 9, 10; Fig. 12, 13, 14, 
15, 16,17). Where the optic nerves enter the optic ganglion (Diagrams 4, 
5, 6; Fig. 11), the cortex is composed of a single layer of small cells 
and the giant cells are surrounded laterally by the cells of this group. 
They are packed in around the giant cells in an irregular line, not 
indicated in the diagrams. It is here impossible to draw a sharp 
line between these brain cells and the cells of the optic ganglion but 
the size and direction helps to define the group; in other sections 
they can be readily distinguished. Postero-laterally, these cells are 
covered by the fibres of the median antero-posterior commissure, some 
fibres undoubtedly originating in these cells. Some cells are directed 
anteriorly, but the majority posteriorly. The pre-central medullary 
area appears in this group; between it and the central area there 
are a few large nerve cells directed anteriorly (Fig. 11). 
Commissure cells. The lateral wall of the post-central medulla 
is formed of medium and large-sized nerve cells, which send their 
processes into the post-lateral commissure (Fig. 13, 14, 15). Ventrally, 
the common post-lateral medulla is separated from the common post- 
central medulla by a group of nerve cells; they are directed anteriorly, 
laterally and posteriorly (Diagrams 9, 10; Fig. 16, 17). 
The giant cell group (Deckzellen). This cell group, found in the 
anterior and dorsal part of the brain near its connection with the 
Anat, Anz. XIIT. Aufsätze. 20 
