OF THE GYRUS MARGINALTS AND GYRUS FORNICATUS IN MONKEYS. 349 
Appendix. 
Received April 22,—Read May 16, 1889. 
On the Degenerations tvhich follow the Removal of the External Motor Cortex, and of 
the tvhole Motor Cortex of One Hemisphere in Monhegs as compared with those 
which follow Lesions of the Ggrus Marginalis alone. 
Since sending in the foregoing paper I have investigated the following cases :— 
A.—Three of removal of the external motor surface of the brain in which the animals 
lived for a considerable time (from two to four months) after the operation.* 
Tiie lesions were so muchlalike, and the resulting degenerations are so similar, 
that it would be superfluous to describe each case separately. 
Sections were cut through the brain obliquely dovv^nwards and forwards 
perpendicular to the fibres of the crusta, and transverse sections of the pons, 
medulla, and of the three regions of the spinal cord were made. 
Degenerations Observed. 
In the internal capside the degeneration is well-marked and constant, occupying 
the side next the lenticular nucleus. The inner side next the thalamus is almost 
entirely normal. The degeneration is greatest in amount about the angle, extending 
over the middle third. 
Crusta .—The degeneration occupies the middle third and is clearly defined, the 
dorsal part being less completely degenerated than the ventral. 
Pons .—The degeneration extends over the whole pyramidal bundles of the same 
side, almost all the fibres being degenerated. 
Medulla .—The whole pyramid on the same side is degenerated, except a narrow 
portion towards the posterior and mesial border, which is less degenerated than the 
rest of the tract. 
Spinal cord .—In the upper cervical region the whole extent of the crossed 
pyramidal tract is degenerated, that part bordering the direct cerebellar tract less 
completely than the rest. The degeneration extends along the circumference, back¬ 
wards towards the posterior root exit, as a gradually narrowing band enclosing the 
direct cerebellar tract, which has an elongated wedge shape. 
In the dorsal region the degenerated tract is entirely separated from the emeum- 
ference by the direct cerebellar tract. It can be followed down the cord as far as 
the lower lumbar region where it is seen as a few degenerated fibres close to the 
circumference and a little external to the posterior root exit. 
* For an account of the symptoms observed during life see “ A Record of Experiments upon the 
Functions of the Cerebral Cortex,” Cases 4, 5, and 8, by Professors Schafer and Horsley, ‘ Phil. 
Trans.,’ B, Yol. 179 (1888), pp. 1-45. 
