744 THE CEREBRAL CORTEX. 



ever, are not confined to the ascending parietal, but extend to the 

 corresponding margin of the ascending frontal, where indeed they may 

 be alone represented. The thumb movements are most marked near 

 the lowermost limit of the area, where, with a very weak excitation, a 

 simple movement of the thumb, or one combined with that of the index 

 finger (opposition), may readily be obtained. 1 



4. The area connected with movements of the lower limb. This 

 (Figs. 336, 338) occupies the upper end of the ascending frontal 

 and ascending parietal gyri (including the parietal lobule) above the 

 arm area, 2 and the corresponding parts of the marginal convolution. 3 

 Immediately in front of it is the area connected with movements of 

 the trunk and tail, which in fact merges gradually into it. Stimulation 

 over the posterior part of the area, namely, the upper end of the ascend- 

 ing parietal gyrus and the parietal lobule, and the adjacent part of 

 the marginal gyrus, produces primarily movements of the opposite toes, 

 which may or may not be associated with that of other parts of the 

 limb. The movements of the hallux are especially represented close to 

 the Kolandic sulcus at the upper end of the ascending frontal gyrus. 4 

 It will be seen, therefore, that a large part of the leg area of the 

 monkey is mainly connected with toe-movements, which indeed, as 

 Ferrier found, are also readily, although not as a primary effect, elicited 

 by stimulation even of the most anterior part of the area. 



The movements of the ankle, knee, and hip are by no means sharply 

 differentiated from one another in the leg area, being generally obtained 

 in association, as indeed is the case in most voluntary movements of the 

 limb. But it will be found that, on the whole, the representation of 

 movements of toes, ankle, knee, and hip is from behind forwards ; hip 

 movements being most readily obtained from the front of the area, toe- 

 movements from the back, and knee- and ankle-movements from the 

 middle part, the hip-movements being frequently combined with move- 

 ments of the tail and of the pelvis. The analysis by stimulation of the 

 leg centre by Beevor and Horsley 5 gave uncertain results as to the focal 

 points for the representation of these movements. They found that in 

 by far the majority of cases the primary movement produced was that 

 of flexion of all three joints, such, it may be added, as occurs when the 

 limb is advanced in climbing. It is often followed, as in that action, 

 by general extension. Extension of the hip, produced by contraction of 

 the gluteal muscles, is more frequently got as a primary movement from 

 excitation of the marginal gyrus near the anterior limit of the leg area, 

 and flexion of the knee produced by contraction of the hamstrings a 

 little behind this. 6 Extirpation of the leg area is followed by, at first, 

 complete paralysis of the limb, which hangs down limp in climbing, is 

 dragged behind in walking, and in sitting is thrust passively forward. 

 In the course of a week or two, however, the condition begins to show 



1 Horsley and Schafer in Festschrift f. C. Ludwig, Leipzig, 1887, S. 286 ; Beevor and 

 Horsley, Phil. Trans., London, 1888, B, p. 232. 



2 Ferrier, Proc. Roy. Soc. London, 1875, vol. xxiii. 



3 Horsley and Schafer, ibid., 1884, vol. xxxvi. p. 437. 



4 Beevor and Horsley, Phil. Trans., London, 1888, B. Both flexion and extension 

 may be excited from the same spot. Sherrington found (in the monkey) that when flexion 

 of the hallux was obtained, if the nerve passing to the flexors was cut, excitation at the 

 same part of the cortex now produced extension. 



5 Phil. Trans., London, 1888, B. 



6 Horsley and Schafer, Festschrift f. C. Ludwig, Leipzig, 1887, S. 278 ; and Phil. Trans., 

 London, 1888, B, p. 10. 



