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PHYSIOLOGY. 



The olfactory region contains the olfactory cells. These possess 

 a body of spindle shape with a large nucleus containing micleoli. In 

 the deeper part the olfactory cells pass into and become continuous 

 with fine fibers. These last pass into the olfactory nerve. 



The olfactory, the nerve of smell, issues by two roots, each from 

 the corresponding hemisphere. The fibers are composed of medul- 

 Jated and nonmedullated fibers. 



These latter fibers proceed from the olfactory bulb. 



Fig. 305. Diagram of the Connections of Cells and Fibers in the 

 Olfactory Bulb. (SCHAFER, in Quain's Anatomy.) 



olf.c, Cells of the olfactory mucous membrane, olf.n, Deepest layer of the 

 bulb, composed of the olfactory nerve-fibers which are prolonged from the olfac- 

 tory cells, gl, Olfactory glomeruli, containing arborization of the olfactory 

 nerve-fibers and of the dendrons of the mitral cells, me, mitral cells, a, Thin 

 axis-cylinder process passing toward the nerve-fiber layer, n.tr, of the bulb to 

 become continuous with fibers of the olfactory tract; these axis-cylinder proc- 

 esses are seen to give off collaterals, some of which pass again into the deeper 

 layers of the bulb, n', A nerve-fiber from the olfactory tract ramifying in the 

 gray matter of the bulb. 



The olfactory buib is a part of the cerebral cortex and is an oval 

 or club-shaped mass of gray matter which rests on the cribriform 

 plate of the ethmoid bone, through the foramen of which it is con- 

 nected with the olfactory nerves. The olfactory nerves are twenty 

 in number and are the central coursing of the neuraxons of the rod- 

 shaped olfactory nerve-cells in the olfactory region of the nose. They 

 pass through the openings in the cribriform plate and terminate in 



