OF DENISON UNIVERSITY. 
5 S 
The following measurements are added : 
Total length, 5 cm.; length of olfactory lobes, 12 mm.; front of 
hemisphere to chiasm, 12 mm.; to posterior third nerve root, 24 mm.; 
to bridge, 26 mm.; to posterior of pons, 33 mm. Total width of cer- 
ebrum at base, 32 mm.; at chiasm, 26 mm.; distance between oppo- 
site sulci rhinales at chiasm, 21 mm.; space between opposite pyriform 
lobes at nearest point, 8 mm ; distance between fifth nerve roots, lO' 
mm.; distance between seventh nerve roots, ii mm.; distance be- 
tween sixth nerve roots, 5 mm.; distance between eighth nerve roots,. 
12;^ mm.; width of cerebellum at widest part, 25 mm.; width of cord 
at base of medulla, 8 mm.; width of medulla near lower end, 13 mm.; 
from anterior of bridge to first spinal nerve, 21 mm.; from anterior of 
bridge to second spinal nerve. 25 mm.; from anterior of bridge to 
third spinal nerve, 30 mm.; median length of hemispheres, 47 mm.; 
width of cerebellum exclusive of vermiform, 22 mm. 
Structure of the cord and medulla. 
The cross sections of the cervical region of the cord of Arctomys 
show the relations of the white and gray matter to be rather primitive. 
The minor subdivision of some of the longitudinal columns can not 
be determined so readily as in higher types. 
The central gray matter divides the cord into the ventral, lateral, 
and dorsal columns. Fig. i, Plate XITI, taken at the entrance of the 
second cervical dorsal roots, shows the relations of these parts. The 
ventral column is rather smaller in comparison to the lateral and dor- 
sal columns. It receives fibres from the ventral cornu, a., and from 
the anterior commissure, b. The lateral column is uniform in texture 
and is not susceptible to a division into pyramidal and direct cerebral 
tracts by any markings on the sections. It receives a constant supply 
of fibres from the whole extent of the ventral column. The dorsal 
columns show a decided difference in texture in different parts and can 
be easily divided into the dorsal or Burdach’s columns, dorsal me- 
dian, or Golfs columns, h. 
In Golfs columns the transverse section shows but a small amount 
of neuroglia and the section is entirely made up of nerve fibres, as 
will be seen from Plate XIII, Fig. 7, while Fig. 6 of the same plate 
shows the structure of Burdach’s columns and the lateral and ventral 
