29 
ganglion consists of a superficial layer of cortical cells and a central 
medulla. 
Cortex. This may be divided into several groups. 
An anterior cell group is found (Fig. 18) at the entrance of the 
optic commissure into the eye. These cells are pyriform, of medium 
size, with their processes extending in the medulla to the median 
line. It is rarely that a cell is seen directed toward the optic 
commissure. 
Two antero-lateral cell groups are seen on each side, opposite 
to the anterior group, extending to the median line. These cells are 
about equal in size to those of the anterior group. They are directed 
toward the optic commissure and the medulla. 
A single, large group of small cells is located posteriorly and 
post-laterally. These cells are several layers deep and their processes 
are directed toward the medulla. 
Between the last two groups, laterally at the surface, the medulla 
approaches the capsule. At this place there is generally found a 
small group of large nerve cells. These cells are entirely distinct in 
shape and appearance from the other cells. Their processes are directed 
inwards. With what part of the ganglion they are connected, I am 
unable to say. 
Dorsally and ventrally, the ganglion is covered by extensions of 
the anterior, antero-lateral and posterior cell groups. Their processes 
enter the medulla at right angles with the surface. The medulla comes 
to the surface dorsally and ventrally in the transverse median line. 
WEISMANN divides the ganglion into two lateral halves, but I 
find no internal indication of a division. When the optic nerves enter 
the ganglion posteriorly they split the posterior cell group into a 
posterior and two lateral groups. The posterior group projects into 
the medulla as a wedge, due to the crowding, but the anterior group 
shows no such formation. No indication of two dorso-lateral lobes 
was noted in serial sections; they may have been obliterated by the 
fixing solution. Around the entire ganglion in the transverse median 
line, the medulla is in intimate relation with the surface, and the ganglion 
could be divided into an anterior and posterior portion. 
The optic commissure. This is formed of fibres which pass between 
the anterior and antero-lateral cell groups and between the individual 
cells of the anterior cell group. They can not be traced to the middle 
line of the medulla. 
The medulla. This is somewhat different from the Punktsubstanz 
of the brain. The processes of the cells extend generally to the median 
20 * 
