OF DENISON UNIVERSITY. 
57 
to coincide with the physiological requirements of the organ. The 
great simplicity of these cells in Arctomys adapts it for their study. 
We incline to accept Beevor’s suggestion in part, i. e., that the ascend- 
ing processes of Purkinje’s cells turn at right angles and connect with 
fibres leading to the brain 
The Mesencephalon. 
We preface our own observations with Stieda’s account of the 
corpora quadrigemina in the rabbit, which is as follows : 
“The peduncular region has the following nuclei. Above the 
united pyramid tracts and lower longitudinal bundles is a cell group 
on either side, each of which consists of two parts. The under (ven- 
tral) portion is the larger and contains many small cells (.012-. 16 mm ) 
in a granular ground mass; the upper, smaller portion has large angu- 
lar cells of .14 mm. diameter. This nucleus may be called Nucleus: 
peduncular is. On the lower margin of the central gray, thus near the 
floor of the aqueduct, is the oculomotor nucleus of either side. It 
consists of cells of moderate size (.04 mm.) and angular form. Be- 
tween the two nuclei and near the floor of the ventricle are numbers 
of small triangular or fusiform cells. The fibres from the oculomotor 
nucleus are very numerous and pass through the nucleus peduncularis 
and between the bundles of the anterior columns to their roots.” 
“ The central gray of the posterior corpora quadrigemina is lim- 
ited by fibre tracts. Laterally the nucleus of the trochlearis is mingled 
with these fibres. [The author’s figures are here derived from the dog^ 
and we are left in doubt as to the condition in the rabbit, though he 
explicitly states in a foot-note elsewhere that he introduces references 
to drawings of other brains that are described only where they are 
similar.] The nerve-fibres of the corpora quadrigemina are partly 
transverse, which decussate in small bundles above the aqueduct, and 
partly oblique bundles.” 
“The central part of the nates is, like the other gray matter, com- 
posed of small nerve cells scattered in a granulate mass, but the super- 
ficial portion exhibits distinct interstratification of a white zone parallel 
to the surface. With high powers an outer zone devoid of cells, may 
be seen ; below this a zone of granulated substance with scattered 
small cells, then a layer of numerous transversely cut bundles of fibres 
separated by gray substance, containing stellate nerve cells (.008-. 012 
mm.) with well-developed processes.”, 
