THE NEOPALLIUM. 353 



the frontal lobe and ending in the occipital lobe. In addition to 

 these tracts which connect distant lobes, within each lobe are 

 numerous association bundles, such as the calcarine, vertical, 

 and transverse bundles in the occipital lobe. These various 

 association bundles are very complex, consisting in most cases of 

 fibers running in both directions and of fibers which enter and 

 leave the bundles at various points of their course. Their grouping 

 into bundles is due merely to mechanical conditions arising from 

 the form of the brain. The greater part of the corpus callosum 

 fibers go to the anterior and posterior association fields; the middle 

 field receives few commissural fibers. 



In order to understand the functions of the association centers 

 it is necessary to define more exactly the functions of the sensory- 

 areas. The phenomena of clear and sharp sense impressions is 

 dependent upon the sense areas. Disease or injury to one of these 

 centers interferes with the clearness and definiteness of the sen- 

 sations with which that area is concerned. At the same time the 

 memory of such sense impressions and percepts formed from 

 several kinds of sense impressions may remain intact. Also, 

 according to Flechsig, the perception of the spatial and temporal 

 relations between sense perceptions depend upon the sense areas. 

 Thus the clear recognition of the form of an object when felt by 

 the hand depends upon the proper functioning of the hand and 

 arm portion of the somaesthetic area, while the memory picture 

 of the same object made up from previous sense impressions 

 (tactile, visual, etc.) is a function of some of the association centers 

 and may be preserved when the somaesthetic area is diseased. 



As the sense areas send fibers into the adjoining border zones of 

 the association fields the participation of these zones will provide 

 for the combination of simple sense impressions into perceptions 

 of sHght complexity. Thus general images of form based upon 

 the examination of various objects by the hand may be localized 

 in the border zone adjoining the sense area for the hand. In 

 some such way the border zones stand in relation with the several 

 sense areas and provide for relatively simple association of sense 

 impressions from nearly related regions of the body. More 

 complex images of the form of objects dependent upon the com- 

 23 



