ASSOCIATION FIBERS. 237 



contiguous parts within circumscribed areas. The richness 

 of the zonal layer of fibers, as already pointed out in describing 

 the plexiform layer of the cortex, varies greatly in different regions, 

 being best developed in the subiculum. The fibers comprising 

 the zonal layer have four sources of origin: (a) The axones and 

 dendrites of the cells of Cajal in the plexiform layer, (b) The 

 apical dendrites of the subjacent pyramids, (c) The T-branched 



Fig. 74. Diagram of association fibers in the cerebral hemisphere. 

 (Gordinier and Quain after Meynert.) 



s. Short association fibers, connecting adjacent gyri. f.l.s. Fasciculus longitudinalis su- 

 perior, c.i. Cingulum. f.p. Fasciculus perpendicularis. f.l.i. Fasciculus longitudinalis in- 

 ferior, f.u. Fasciculus uncinatus. fo. Fornix. fi. Crus fornicis. v.d'A. Thalamo-mammil- 

 lary bundle of Vicq d'Azyr. 



axones of Martinotti's cells, (d) The corticipetal axones which 

 terminate in the superficial layer of the cortex. 



The short association fibers are almost infinite in their con- 

 nections. They connect the receptive and psychic sensory areas, 

 and their interruption on the left side causes inability to interpret 

 the sensations, called mind-blindness, mind-deafness, stere- 

 agnosis, etc. Again, those short fibers also associate the psychic 

 with the psychic-motor, and the psychic-motor with the emissive- 



