SENSE AREAS AND ASSOCIATION AREAS. 



205 



hippocampal lobes or other gray matter belonging to the rhinen- 

 cephalon. (2) The mesial bundle, the fibers of which terminate 

 in the gray matter adjacent to the base of the olfactory tract, 

 the tuberculum olfactorium, whence the path is probably continued 

 by other neurons to the region of the hippocampal lobe. (3) The 

 lateral tract, whose fibers seem to pass to the hippocampal lobe of 

 the same side. According to Van Gehuchten,* none of the fibers 

 of the anterior commissure arise from the nerve cells in the olfactory 

 bulb. He considers that the fibers in the olfactory portion of this 

 commissure constitute an association system connecting the olfac- 

 tory lobe of one side with the olfactory bulb of the other side. 



\ 



Fig. 90. Diagram of the central course of the olfactory fibers: /, Olfactory bulb; 

 II, olfactory tract; ///, cortex of the hippocampal lobe (gyfus uncinatus); IV, anterior 

 commissure, olfactory portion; A, olfactory epithelial cells of nose (their fibers, olfactory 

 nerve fibers, terminate in the glomeruli of the bulb) ; B, glomeruli of olfactory bulb where 

 the olfactory fibers come in contact with the dendrites of the. mitral cells; C, mitral and 

 brush cells; 1, 2, 3, axons from the mitral cells constituting the fibers of the olfactory 

 tract. Fibers 3, which enter the commissure, arise, according to some observers, from 

 cells in the olfactory lobe near the base of the tract. 



The Cortical Center for Smell. So far as the histological 

 evidence goes, it tends to show that the chief cortical termination 

 of the olfactory paths is 'found in the hippocampal lobe, especially 

 its distal portion, the gyrus uncinatus. The experimental evi- 

 dence from the side of physiology points in the same direction. 

 .Ferrier states that electrical stimulation in this region is followed by 



* Van Gehuchten, "Le NeVraxe," 6, 191, 1904. 



