1906-7.] Experimental Lesions in Motor Cortex of Monkey. 299 
In some o£ these cases, however, the degeneration could not be satisfactorily 
followed in the parts of the brain above the mesencephalon on account 
of the imperfect penetration of the staining fluid. 
Summary and Conclusions. 
In endeavouring to trace the course of the individual portions of the 
pyramidal tract we find that our results agree, for the most part, with 
those obtained by the majority of former observers who have employed 
the degeneration method with Marchi staining. The fibres arising from 
the giant pyramidal cells of the motor cortex pass into the corona radiata, 
at first in fairly distinct groups, but they soon begin to intermingle, and 
in the highest levels of the internal capsule there is already considerable 
overlapping. Those from the lateral portion of the Rolandic area (face) 
enter the capsule most anteriorly, those from the mesial portion (leg area) 
most posteriorly, while between the two, but intermixing with them, come 
the fibres from the intermediate parts of the cortex, viz. the arm and trunk 
areas. In passing down through the internal capsule into the pes pedun- 
culi the tract becomes compressed within narrower limits, and this inter- 
mingling of the fibres from the different areas becomes more marked. In 
the lower levels of the capsule the fields of degeneration resulting from 
ablation of the face, trunk and limb areas overlap, to a very large extent, 
and this is more marked still in the crusta (figs. 3 and 4). Below this, in 
the pontine pyramidal bundles, the anterior pyramids, and the direct and 
crossed pyramidal tracts in the spinal cord, there is no localisation of fibres 
at all, the degeneration following the most limited lesion being uniformly 
scattered over the entire area of the pyramidal tract in transverse section. 
With regard to the longitudinal localisation of the fibres in the tract, our 
results partly support those of Sherrington.* He found that after lesions 
in the leg area, encroaching little, if at all, on the arm area, the degenera- 
tion in the cord stopped short in great part in the cervical enlargement ; 
and after lesion in the arm area, encroaching little, if at all, on the leg 
area, the degeneration in the cord extended down through the thoracic into 
the lumbar, and even throughout the sacral region. He concluded from 
this that the pyramidal tract is a path of cortical visceral (splanchnic) as 
well as of cortical somatic fibres, — hence fibres descending from the arm 
area of the cortex into the lumbar region of the cord. We have not 
found that after pure leg area lesions a great part of the degenera- 
tion ends in the grey matter of the cervical region, or that a great number 
of fibres can be followed down to the lumbar region after lesions con- 
* Sherrington, Jour, of Physiol., vol. x. (1889), p. 429. 
