STIMULATING THE MOTOR CORTEX IN ANIMALS. 735 



which are eventually manifested are those which are " associated " with 

 the movements of the side of the body opposite to that which is 

 paralysed, and appear to be brought about by the action of the other 

 side of the brain acting through commissural fibres in the lower level 

 centres. 1 The more delicate movements of the fingers and toes, which 

 are never thus associated on the two sides, never reappear. 



It is especially after removal of the leg area of the cortex that the 

 associated movements become so completely restored, that, on superficial observa- 

 tion, it is almost impossible 

 after a few weeks to detect 

 any motor paralysis. But if 

 the animal be held by the 

 upper part of the body and 

 swung gently forward to- 

 wards the wire-work of a 

 cage, or lowered rapidly 

 towards the ground, the leg 

 on the same side as the 

 lesion will be put forward 

 or downward to catch hold 

 of the cage or touch the 

 ground, but never the leg 

 on the opposite side, how- 

 ever long the animal may 

 have been kept after the 

 lesion. This is, in fact, a 

 true voluntary movement, 

 and it is not recovered, while 

 all the associated movements 

 which are used in ordinary 

 progression have resumed 



to all appearance their nor- 

 mal characters. 



In the same way it was 

 shown by Hitzig that a dog 

 from which the left sigmoid 

 gyms had been removed 

 would, if suspended in the 

 air by a cloth round its 

 body, its legs being left 

 free, immediately withdraw 

 the left limbs, on a needle 

 being brought near them as 

 if for the purpose of prick- 

 ing them ; but although, on 



FIG. 335. Diagram showing the results obtained by 

 Ferrier from electrical excitation of the cerebral cortex 

 of the monkey. 1, The opposite hind-limb is advanced 

 as in walking. 2, Flexion with outward rotation of 

 the thigh, rotation inwards of the leg, flexion of the 

 toes. 3, Movements similar to 1 and 2, and in some 

 cases also the tail is moved. 4, The opposite arm is 

 adducted, extended, or retracted, the hand pronated. 

 5, Extension forwards of opposite arm. a, b, c, d, 



Flexion of the fingers and clenching of the fist. 6, 

 Flexion and supination of forearm. 7, Retraction and 

 elevation of the angle of the mouth. 8, Elevation of 

 the ala of the nose and upper lip. 9 and 10, Opening 

 of the mouth with protrusion of tongue at 9, and 

 retraction at 10. 11, Retraction of the angle of the 

 mouth. The action is that of the platysma inyoides. 

 12, The eyes open widely, the pupils dilate, and head 

 and eyes turn to the opposite side. 13, 13', The eyes 

 move to the opposite side with an upward or down- 

 ward deviation, according as the electrodes are on 13 

 or 13' respectively ; normally also the pupils become 

 contracted. 14, 14', Pricking of the opposite ear, 

 head and eyes turn to the opposite side, pupils dilate 

 widely. 15 (not shown in diagram), on the hippo- 

 campal gyms (anterior and inner aspect), torsion of 

 the lip and semiclosure of nostril of same side. 



approaching the right limbs 

 with the needle, the animal showed signs of apprehension, these limbs were 

 never moved away by themselves, nor except as a general movement and in 

 association with those of the opposite side. 



The areas, excitation of which on one side of the brain produces in 

 the monkey movements involving muscles on both sides of the body, 

 are (1) The area for movements of the head and eyes ; (2) the area 

 concerned with movements of the tongue and cheeks, and movements 

 of mastication and swallowing ; (3) the larynx area ; (4) the area 



1 Broadbent, Brit, and For. Med.-Chir. Rev., London, 1866, p. 477. 



