SENSE AREAS AND ASSOCIATION AREAS 



217 



are acted upon by the olfactory stimuli, and the impulses thus 

 aroused are conveyed by the basal processes of the cells, the olfac- 

 tory fibers, through the cribriform plate of the ethmoid bone into 

 the olfactory bulb. 



The Olfactory Bulb and its Connections. The olfactory 

 bulbs are outgrowths from and portions of the cerebral hemi- 

 spheres. Each bulb is connected with the cerebral hemispheres 

 by its olfactory tract. The connections established by the fibers 



Fig. 96. Diagram of the central course of the olfactory fibers: /, Olfactory bulb} 

 77, 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. 



of this tract are widespread, complicated, and in part incom- 

 pletely known. All those portions of the brain connected with the 

 sense of smell are sometimes grouped together as the rhinenceph- 

 alon. According to von Kolliker, the parts included under this 

 designation are, in addition to the olfactory bulb and tract, Am- 

 mon's horn, the fascia dentata, the hippocampal lobe, the f ornix, the 

 septum pellucidum, and the anterior commissure. The schematic 

 connections of the olfactory fibers are as follows (Fig. 96) : After 

 entering the olfactory lobe the fibers terminate in certain globular 

 bodies, the glomeruli olfactorii (B), whose diameter varies from 0.1 to 

 0.3 mm. Here connections are made by contact with the dendrites 



