35 



NERVOUS SYSTEM OF VERTEBRATES. 



Fig. 177. The primordial areas and the border zones of the association fields, 

 lateral surface. From Flechsig. The figure represents the extent of myelin- 

 ization in the hemisphere of a newborn infant 54 cm. in length. The primary 

 sense areas and a part of the border zones are myelinated and the numerals indicate 

 the order in which they receive their myelin. The anterior and posterior associ- 

 ation fields stand out sharply as light areas. The middle association field is 

 exposed to view by drawing aside the temporal lobe. 



Fig. 178. The primordial areas and the border zones of the association fields, 

 mesial surface. From Flechsig. See Fig. 177. 



