1 906-7. j Experimental Lesions in Motor Cortex of Monkey. 301 
these authors in the human subject, but we are inclined rather to believe 
that they terminate in the substantia nigra and in the tegmentum behind 
it, as we cannot pick them up again in the fillet in sections of the pons 
made at a lower level.* Such fibres ending in the grey matter of the 
anterior corpora quadrigemina have been described in the cat and dog, and 
by Horsley and Beevor j- in the monkey. 
We have never been able to trace fibres from the pyramidal tract to 
any of the cranial motor nuclei, and have found no evidence of fine or 
terminal degeneration in the neighbourhood of these nuclei. 
In the monkey we have never seen any trace of a ventro-lateral 
pyramidal tract, such as is described by Barnes j in the human subject. 
This tract is said to be given off frequently in man : it may arise in the 
pons, medulla oblongata, or first cervical segment, and it passes down in 
the region of Helweg’s tract on the ventro-lateral aspect of the inferior 
olivary nucleus. Barnes claims that it is distinct from Helweg’s tract ; it 
is best marked in the upper two cervical segments, but occasionally he has 
succeeded in tracing it to the lumbo-sacral region. We find nothing to 
represent it in the monkey, neither are there any fibres corresponding to 
Pick’s bundle, another aberrant strand which is sometimes found in the 
pyramidal system in man. 
In the spinal cord the passage of collateral fibres from the crossed 
pyramidal tract, first described by Schafer § (and in some cases from the 
homolateral), is very evident both in the cervical and lumbar enlargements, 
and to some extent in the thoracic region. They are seen in transverse and 
in longitudinal sections of the cord, and terminate in the grey matter at 
the base of the posterior horn. The fine degeneration in this region of the 
grey matter is very abundant : the corresponding region of the opposite 
side is free, and the contrast between the two sides in this respect, in the 
same section, is very marked. 
Fibres representing a direct anterior pyramidal tract are found in the 
first cervical segment only ; the direct lateral can be traced to the lower end 
of the sacral region, and the crossed pyramidal to the first coccygeal segment. 
The expenses incurred in this research were defrayed by grants from the Moray Fund 
and from the Carnegie Trust. 
* In some of our sections through the pons we did find a few scattered fibres along the 
anterior margin of the fillet. 
t Horsley and Beevor, Brain , vol. xxv. (1902), p. 436. | Barnes, loc. cit. 
§ Schafer, Jour, of Physiol ., vol. xxiv., p. xxii — Proceedings of the Physiol. Soc. 
( Issued separately October 3, 1907.) 
