SENSE AREAS AND ASSOCIATION AREAS. 



203 



of nerve cells of the olfactory lobe, the mitral and brush cells (C). 

 The axons of these cells pass toward the brain in the olfactory tract. 

 Three bundles of these fibers are distinguished: (1) The precommis- 

 sural bundle, the fibers of which terminate in part in nerve cells sit- 

 uated in the tract itself, but, for the most part, enter the anterior 

 commissure and pass to the same or the opposite side, to end in the 

 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, 



Fig. 91. Diagram of the central course of the olfactory fibers: /, Olfactory bulb; 

 //, olfactory tract; ///, cortex of the hippocampal lobe (gyrus 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 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. 



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



