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on the homolateral side than in the case of total extirpation. The only 
noteworthy point is the fact that although the cortical lesion was limited 
to the leg area, a few fibres can be seen to enter the grey matter of the 
cord in the cervical enlargement, and the motor tract suffers some loss as 
it traverses this region. In the thoracic region the diminution in the 
number of fibres is very slight, but in the lumbar region they disappear very 
rapidly, and can be seen to enter the grey matter and to terminate in a 
copious fine degeneration at the base of the posterior horn. The crossed 
tract can be traced to the last sacral segment, and the homolateral fibres 
end one or two segments higher up. 
Degeneration following Extirpation of the Arm Area. 
The lesion does not include the whole arm area, that portion of the 
cortex next to the body area having escaped injury (fig. 1). Association 
and commissural fibres are found radiating from the region extirpated; 
these consist mostly of fine fibres, the great majority of the coarse fibres 
mixed with fine passing into the corona radiata, and thence to the internal 
capsule. In the upper regions of the capsule they extend farther forward 
than the fibres from the leg area, intermingling with the latter posteriorly, 
but in the lower levels the fibres from the two areas overlap to a 
great extent. A large proportion of the fine fibres end in the optic 
thalamus. 
In transverse sections of the mid-brain through the anterior corpora 
quadrigemina (fig. 4) the degeneration occupies about two-fifths of the 
crusta, the mesial fifth and lateral two-fifths containing only a few 
scattered fibres, but these are more numerous in the former than in the 
latter. The area of densest degeneration lies distinctly on the mesial 
side of the middle point of the crusta, and from this it fades away on 
either side. Some fine degeneration can be seen in the substantia nigra 
behind the crusta, but no fibres can be traced into the tegmentum. 
Throughout the pons and medulla oblongata the degeneration is very 
similar to that already described for the leg area, differing from it only in 
a few minor details. The mesial (fronto-pontine) and lateral (temporo- 
pontine) bundles in the pons contain only a few scattered fibres, and 
some isolated fibres are to be seen along the anterior margin of the mesial 
fillet, but they are not intermixed with the fillet fibres. In the medulla 
oblongata the degeneration is scattered uniformly over the entire area of 
the pyramid, and after the decussation the proportion of crossed to un- 
