OF THE GYRUS MARGINALIS AND GYRUS FORNICATUS IN MONKEYS. 337 
and is nearer the circumference, leaving, however, a band of healthy fibres in the 
position of the direct cerebellar tract. 
Degenerated fibres and slight sclerosis can be seen with the microscope on the same 
side (left) as the lesion in a similar position. 
Lumbar Enlargement .— The degeneration here is less in amount. It occupies the 
angle between the posterior root and the circumference. A few degenerated fibres can 
be seen in a similar position on the same side as the lesion. 
Case 2.— No. 12 of First Series. (Figs. 2a to 2d, Plates 27 and 28.) 
Lesion. —Ablation of the posterior three-fourths of the left marginal convolution and 
an adjoining strip of the external surface as far as sulcus x (tig. 2a). The gyrus 
fornicatus was also somewhat injured. 
Result .— Paralysis of the right side of the trunk and right leg, and partial paralysis 
of the right arm, which had imperfect power of extension from the shoulder. 
This animal was killed six months after the ojoeration. 
Degenerations Observed. 
The pieces from which sections were cut showed, even with the naked eye, well 
marked degeneration in the pyramidal bundles in the pons and medulla on the same 
side as the lesion, and in the spinal cord in the crossed pyramidal tracts of both sides, 
although much more obviously on the side opposite the lesion. 
Medulla .— There is well marked, scattered degeneration in the left pyramid 
(fig. 2b), with considerable shrinking and sclerosis. 
Sg)inal Cord.—Cervical Region. —There is a marked triangular patch of degenera¬ 
tion in the crossed pyramidal tract on the right side, denser where it borders the 
direct cerebellar tract, and reaching the circumference near the middle of the lateral 
border, where it spreads both backwards and forwards, but especiall}^ the latter, 
involving the outer part of the direct cerebellar tract. 
In a section at the level of the second cervical nerves (fig. 2c) a band of degeneration 
is seen close to the circumference, extending from the posterior root exit to where the 
pyramidal tract degeneration reaches the circumference. On the left side there is a 
small amount of degeneration, scattered over a similar area, and on both sides there is 
sclerosis in the degenerated areas. 
Dorsal Region.— Ax the level of the fourth nerves (fig. 2d) the degeneration is very 
well defined. It extends from the apex of the posterior cornu (light side) outwards 
and forwards as a diminishing strip, till it reaches the surface about the anterior end of 
the direct cerebellar tract. I'here is also a little deo-eneration alono- the external border 
O O 
of the direct cerebellar tract, which spreads along the circumference less than in the 
MDCCCLXXXIX.-B. 2 X 
