1903.] On the Cerebral Cortex of the Anthropoid Apes. 155 



readily excitable by faradisation. Its reactions do not appear to 

 differ obviously in this respect from those obtainable from the adult. 

 The movements it yields are not choreiform in character. 



The spinal degeneration ensuing upon ablation of the arm area of 

 the motor cortex of the chimpanzee, although it sometimes reveals a 

 large uncrossed ventral pyramidal tract (direct Py. Tr.), does not 

 do so in every case. Even after bilateral arm area lesions, the ventral 

 . pyramidal degeneration in the spinal cord may be very slight. The 

 anthropoid cord resembles the human, therefore, not only in the 

 possession of this tract, but in exhibiting in regard to it a remarkable 

 degree of individual variation of development as Flechsig showed to be 

 the case in- man. 



The expenses of this research have been in part defrayed by a grant 

 kindly allowed by the Scientific Grants Committee of the British 

 Medical Association. 



DESCRIPTION OF FIGURE. 



Braiu of a chimpanzee (Troglodytes w'ger). Left hemisphere; mesial surface. 

 The extent of the " motor " area on the free surface of the hemisphere is indicated 

 by the black stippling. On the stippled area " LEG," indicates that movements of 

 the lower limb are directly represented in all the regions of the "motor" area 

 visible from this aspect. Such mutual overlapping of the minuter sub-divisions 

 < lists in this area that the diagram does not attempt to exhibit them. The 

 pointing line from " Anus, etc.," indicates broadly the position of the area whence 

 perineal movements are primarily elicitable. 



Kulc. Central. = central fissure. Sulc. calcarin. = calcarine fissure. Sulc. 

 (nirieto occip. = parieto- occipital fissure. Svlc. calloso marg. = calloso-rnarginal 

 fissure. Sulc. precentr. niarg. pre-central marginal fissure. 



The single italic letters mark spots whence, occasionally and irregularly, move- 

 ments of the foot and leg (ff), of the shoulder and chest (*), and of the thumb 

 and fingers (h) have been evoked by strong faradisation. Similarly the shaded area 

 inarked " EYES " indicates a field of free surface of cortex which under 

 a nidi sat ion yields conjugate movements of the eyeballs. The conditions of 

 obtainuient of these reactions separates them from those characterising the 

 " motor " area. 



