1906-7.] Experimental Lesions in Motor Cortex of Monkey. 293 
In the 7th cervical segment (fig. 10), and more so in the 8th, the dorsal 
cerebellar tract extends farther forward still, and separates the crossed 
pyramidal tract from the periphery almost completely, but many fibres 
can be seen detached from the main mass invading the area of the cere- 
bellar tract, particularly at its anterior extremity. In these segments the 
area of degeneration no longer abuts against the grey matter; a clear 
space intervenes between. Through this many degenerated fibres can 
be seen to extend forwards and inwards, and to enter the grey matter 
at the base of the posterior horn, and in this region of the grey matter 
an abundant fine degeneration is evident. The contrast is marked between 
this region and that of the opposite side, in which there is no fine 
degeneration. In transverse sections these fibres which enter the grey 
matter are cut obliquely, but in longitudinal sections they can be seen 
Fig. 12. — Sixth thoracic. 
to come off from the main mass of fibres and to follow a slightly downward 
course before passing into the grey matter. 
In the ls£ thoracic segment (fig. 11) the area of degeneration has greatly 
diminished ; it is almost completely cut off from the periphery by Flechsig’s 
tract — more completely than in the cervical region — and fibres cut obliquely 
are seen to pass into the grey matter, to form there a copious fine degenera- 
tion, as in the cervical enlargement. 
In the mid and louier thoracic segments — the 4th, 6th, and 10th seg- 
ments were examined — (fig. 12), these fibres are not visible, and the amount 
of fine degeneration in the grey matter is very slight. The area of de- 
generation slowly diminishes in sections from above downwards, gradually 
coming nearer to the surface, until in the 10th thoracic segment (fig. 13) 
it touches the periphery of the cord in front of the postero-lateral fissure. 
In the lumbar enlargement (figs. 14 and 15) — sections from the 3rd and 
5th lumbar, and from all the sacral segments were examined — the degenera- 
tion lies close to the periphery at the posterior part of the lateral column, 
just in front of the entering posterior root ; it rapidly diminishes in success- 
ive sections from above downwards. The homolateral fibres can be traced 
