1906-7.] Experimental Lesions in Motor Cortex of Monkey. 295 
on the mesial aspect of the hemisphere had been only slightly involved in 
the lesion. The degeneration, however, was found to be almost as exten- 
sive as in the first case, and to show practically identical features, so that 
a description of this second case is not necessary. 
Degeneration following Lesions in the Leg Area. 
We first extirpated the whole leg area without encroaching on the 
arm and trunk areas. This included the upper portion of the precentral 
convolution above the superior genu of the fissure of Rolando on the 
lateral aspect, with a corresponding portion of the marginal convolution 
on the mesial aspect of the hemisphere (fig. 1). The lesion was made on 
the right side. 
In the internal capsule the degeneration occupies the posterior half or 
three-fourths of the thalamo-lenticular portion of its posterior limb, its 
anterior extremity not reaching to the genu (figs. 2 and 3). The retro- 
lenticular portion of the posterior limb is not free from degeneration, but 
it consists mainly of fine fibres. There is an abundant fine degeneration 
in the lateral nucleus of the thalamus, as in the other cases examined. 
In the mesencephalon the main mass of degeneration lies in the inner 
portion of the lateral half of the crusta (fig. 4). The mesial half is free, 
but the outer portion of the lateral half contains a few degenerated fibres. 
The point of greatest concentration lies somewhat on the mesial side of 
the junction of the outer and middle thirds, and from this the degenera- 
tion shades off on either side. On the posterior aspect of the degeneration 
in its outer portion there are a few small detached bundles of degenerated 
fibres, and a considerable number of single fibres pass backwards through 
the substantia nigra (in which some of them end) into the tegmentum, 
but they cannot be traced very far, and there is no fine degeneration in 
the anterior colliculus. 
Throughout the pons the area covered by the degeneration is practi- 
cally the same as that already described after extirpation of the entire 
motor region, except that the degenerated fibres are less numerous. The 
lateral and mesial bundles are not free, but they contain fewer fibres than 
the middle bundles. Along the anterior margin of the mesial fillet a few 
scattered fibres are to be seen ; these may represent the accessory fillet of 
von Bechterew described by Hoche, Barnes, and others in the human subject. 
Below the pons, in the medulla oblongata and spinal cord the degenera- 
tion is evenly scattered over the entire area of the anterior pyramid and 
crossed pyramidal tract. A slightly greater proportion of fibres remain 
