10 
PROFESSORS V. HORSLEY AND E. A. SCHAFER 
muscles moving the upper part of the trunk may be produced, causing a rotation and 
arching of the dorsal spine (the convexity to the opposite side), but the etfect 
frequently extends also to the lower part of the spine. Superiorly some of the 
muscles which pass from the spine to the scapula may also be thrown into action, and 
inferiorly some of those which pass from the pelvis to the lower extremity, especially 
the glutijei. 
But the effects upon the lower spine and hip muscles more often result from 
excitation at a point a little further back, about opposite the posterior end of the 
furrow X. Excitation of this point also almost invariably produces, besides the 
rotation and arching of the lower spine and the pelvis and extension of the hip, which 
have just been mentioned, movement of the tail to the opposite side and flexion at 
the knee, the last-named movement being caused by contraction of the hamstrings. 
Diagram II. 
At a point slightly farthei back, opposite the upper end of the ascending frontal 
convolution, the flexion of the knee is the most constant result of excitation, but it is 
often combined with eversion of the foot, and sometimes with flexion of the foot.''' 
Finally, at the posterior extremity of the convolution, we have usually obtained as 
the primary result of a weak excitation flexion of the foot and extension of the toes, 
but other muscles of the leg and foot than those concerned in these movements, and 
especially the hamstrings, may also be brought into action. 
Looking, as a whole, at the results of stimulation of the excitable portion of the 
marginal gyrus, it would appear that the application of the electrodes at successive 
points from before backwards produces (1) movements of the head ; (2) of the forearm 
and hand ; (3) of the arm at the shoulder ; (4) of the upper (dorsal) part of the 
* By " flexion of the foot " dorsal flexion is meant. 
