THE RHINENCEPHALON 



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ments of the olfactory nerve, which pass through the cribriform plate of the eth- 

 moid bone and immediately enter the olfactory bulb (Fig. 207). Here they 

 form a feltwork of interlacing fibers over that surface of the bulb which is in 

 contact with the cribriform plate. 



The olfactory bulb of man is solid, and the original cavity is represented by a 

 central gray mass of neuroglia. This is surrounded by a deep layer of myelinated 



Fig. 207. Diagram showing the direction of conduction in the olfactory nerve bulb and tract: 

 A, lateral olfactory stria; B, anterior portion of the anterior commissure; C, bipolar cells of the 

 olfactory mucous membrane. (Cajal.) 



nerve-fibers passing to and from the olfactory tract. Superficial to this are several 

 layers of gray matter of very characteristic structure, and this, in turn, is covered 

 with the superficial layer of unmyelinated fibers from the olfactory nerve fila- 

 ments. Within the gray matter of the bulb are found three types of neurons, 

 the mitral, tufted, and granule cells. The large mitral cells are the most char- 



