1906-7.] Experimental Lesions in Motor Cortex of Monkey. 285 
destroyed by a thermo-cautery, the depth of the lesion being presumably 
sufficient to cauterise the grey matter entirely without damaging the under- 
lying white matter to any appreciable extent. In some cases the lesions 
were more extensive, and involved the cortical area for the entire limb 
(arm or leg), and in one case the whole and in another almost the whole of 
the motor cortex, both on the lateral and mesial aspects. The extirpation 
was made on the left side in some instances, and on the right in others. 
After replacing the dura mater, the scalp wound was closed with horse -hair 
sutures and sealed with a collodion dressing. The operations were carried 
out with the strictest aseptic precautions, and in every case the wounds 
healed by first intention. 
The animals were allowed to live for a period of three weeks after the 
operation, during which time the symptoms following the lesions were 
observed and recorded. At the end of that time they were killed by an over- 
dose of chloroform, and the brain and spinal cord of each removed and placed 
in a large quantity of a 8 per cent, solution of potassium bichromate for three 
weeks, with frequent changing of the fluid. Before it was cut into slices 
to be stained by the March! method, the brain was photographed in order 
to show the position and the superficial extent and depth of the lesion. 
In staining, Busch’s modification of the Marchi method was used in 
a few of our earlier cases, but in our experience the results obtained were 
not always entirely satisfactory, and subsequently we employed Van 
Gehuchten’s modification of this method.* The fluid used by him consists 
of a mixture of a 1 per cent, solution of osmic acid and a 3 per cent, 
solution of potassium bichromate, in the proportion of 1 part of the former 
to 4 parts of the latter. The tissue is allowed to remain in the fluid for 
three weeks; better penetration is claimed for the weaker solution of 
osmic acid acting for a longer time, and this we found to be the case. The 
segments, after staining, were imbedded and cut in either colloidin or 
paraffin, and sections were made at different levels extending from the 
corona radiata to the lower extremity of the spinal cord. 
Results obtained. 
As it has been shown by Sherrington f and by ourselves J that the 
directly excitable motor cortex in the monkey is less extensive than was 
formerly supposed, and as in all previous extirpations, so far as we know, 
* Van. Gehuchten, Systeme nerveux da I’homme, 4th ed., 1906, p. 340. 
t Sherrington, The Integrative Action of the Nervous System , 1906, p. 297. 
+ Proc. Roy. Soc. Edin., vol. xxvii., pt. i., p. 64. 
