SENSE AREAS AND ASSOCIATION AREAS. 213 



I. Primary areas. 



la. Primary projection areas (1, 2, 4, 5, 6, 7, 8 (15), seven or 

 eight in number, and provided with projection fibers 

 sensory and motor. 



I&. Primary areas without projection fibers (3, 9, 10, 11, 12, 13} 

 and apparently without association fibers. Functions un- 

 certain. 

 II. Association areas. 



II* Intermediate or border areas, 14, 16-33, provided with 

 short association fibers. 



II 6 ' Terminal or central areas, 34, 35, 36, provided with long 

 association fibers. 



The Corpus Callosum. The corpus callosum is the most 

 conspicuous of the bands of commissural fibers that connect one 

 cerebral hemisphere with the other. Similar tracts of the same 



Fig. 97. Diagram to show the composition of the corpiis callosum as a system of com- 

 missural fibers, without projection fibers. (Cajal.) 



general nature are the anterior commissure, the fornix, the 

 psalterium, etc. The position and great development of the corpus 

 callosum has made it the object of experimental as well as anatomical 

 investigation. When the corpus is divided by a section along the 

 longitudinal fissure (v. Koranyi) no perceptible effect of either a 

 motor or sensory nature is observed in the animal. When it is 

 stimulated electrically (Mott and Schafer) from above symmetrical 

 movements on the two sides of the body may be obtained. If 

 the motor cortex on one side is removed stimulation in the longi- 

 tudinal fissures causes movements only on the side controlled 

 by the uninjured cortex. These facts are in harmony with the 

 results of histological studies, which indicate that the fibers of the 

 corpus callosum do not enter directly into the internal capsules 

 to be distributed to underlying portions of the brain, but are truly 



