THE CEANIUM. 



1361 



followed by severe paralysis of the hand, but the use and power of the hand is 

 ; regained in a few weeks ; ablations, on the other hand, of even large portions of 

 she posterior central gyrus do not give rise even to transient paralysis. 



In some of the animals experimented on, the motor area was found to extend 

 I to the deeper part of the posterior wall of the central sulcus of Eolando. Anteriorly 

 i it extended into the pre-central sulci as well as into the occasional sulci which cross 

 i the anterior central gyrus ; indeed the hidden part of the motor area fully equals in 



FIG. 1067. CRANIO-CEREBRAL TOPOGRAPHY. 



Shows relations of the motor and sensory areas to the gyri, and to Chiene's lines. 

 Glabella. C. Mid-point of AB. 



External occipital protuberance (inion). CD is drawn parallel to AM. 



Mid-point between G and 0. Z. Post-auricular point. 



Mid-point between M and 0. VW. Guide to anterior limit of transverse sinus. 



Mid-point between T and 0. Y. Tympanic antrum. 



X 1 . 



Zygomatic process of frontal. 

 Root of zygoma (pre-auricular point). 

 Mid-point of EP 

 Mid-point of PS r 



Site at which subarachnoid space may be opened. 

 X 2 . Site for draining lateral ventricle (Kocher). 

 X 3 . Site for draining lateral ventricle (Keen). 



extent that contributing to the free surface of the hemisphere. The motor areas 

 ^xtend a little in front of the superior and inferior pre-central sulci, which cannot 

 therefore be regarded as physiological boundaries. 



Reference to Fig. 1068 shows that, of the main areas, that for the lower extremity 

 occupies the upper third of the motor region, that for the upper extremity the 

 i middle third, while the face occupies the inferior third. The relative topography 

 of the chief subdivisions of these main areas is shown in Fig. 1069. It must be 

 remembered, however, that there exists much overlapping of the adjacent areas. 



The body of the lateral ventricle, which is equal in length to the posterior 



87 



