1906-7.] Experimental Lesions in Motor Cortex of Monkey. 287 
pass to the neighbouring convolutions of the frontal and parietal lobes. 
No attempt was made to trace them to the cortex in the occipital and 
temporal lobes. A considerable number of fibres, mainly fine, cross through 
the corpus callosum to the opposite hemisphere, and many of these can 
be followed to the precentral convolution of that side. The coarse fibres, 
and also many of the fine, after crossing, turn downwards in the corona 
radiata, and probably pass into the internal capsule of the opposite side. 
Most of the coarse fibres, with a large intermixture of medium and 
Fig. 2. — Horizontal section through right cerebral hemi- 
sphere cutting fibres of internal capsule transversely ; 
upper level. This, and the subsequent figures, show 
the extent of the degeneration following total destruc- 
tion of the right motor cortex exclusive of the “head 
and eyes ” area. 
fine fibres, pass into the corona radiata of the same side, and can be 
followed downwards into the internal capsule. In the upper levels of the 
capsule in horizontal sections * (fig. 2) the degeneration covers a wide 
area. This area extends from a point about the middle of the lenticulo- 
striate portion (corresponding to the anterior limb at a lower level) 
anteriorly, to a point a littie behind the posterior extremity of the putamen 
posteriorly (fig. 2). The degenerated fibres are most numerous in the 
anterior half of the thalamo-lenticular portion of the capsule, gradually 
becoming fewer both behind and in front of this. There is a 
* The section described corresponds to a horizontal plane passing through the lenticular 
nucleus a little below its upper surface. It includes the head and a large part of the body 
of the caudate nucleus. 
